FERROMAGNET

BACKGROUND

[0001] Embedded memory with state retention can enable energy and computational efficiency. However, leading spintronic memory options, for example, spin transfer torque based magnetic random access memory (STT-MRAM), suffer from the problem of high voltage and high write current during the programming (e.g., writing) of a bit-cell. For instance, large write current (e.g., greater than 100 mA) and voltage (e.g., greater than 0.7 V) are required to write a tunnel junction based magnetic tunnel junction (MTJ). Limited write current also leads to high write error rates or slow switching times (e.g., exceeding 20 ns) in MTJ based MRAM. The presence of a large current flowing through a tunnel barrier leads to reliability issues in magnetic tunnel junctions. Current fabrication of magnetic junctions use a synthetic anti-ferromagnet (SAF) on the top of the fixed or pinned magnet of the junction. SAF is used as a reference layer to minimize dipolar interactions induced between the SAF and a free magnet layer of the magnetic junction. However, fabricating the SAF is a challenge. For example, the SAF may require high quality atomic crystallinity for its formation, may require a precise thickness of one or more of its layers to exhibit its behavior, and may demand a low level of roughness for its fabrication.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The embodiments of the disclosure will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the disclosure, which, however, should not be taken to limit the disclosure to the specific embodiments, but are for explanation and understanding only.

[0003] Fig. 1A illustrates a magnetization response to an applied magnetic field for a ferromagnet.

[0004] Fig. IB illustrates a magnetization response to an applied magnetic field for a paramagnet.

[0005] Fig. 2 illustrates a device having an out-of-plane magnetic tunnel junction

(MTJ) stack coupled to a spin orbit coupling (SOC) interconnect, where the MTJ stack includes a synthetic anti-ferromagnet (SAF).

[0006] Fig. 3 illustrates a cross-section of the SOC interconnect with electrons having their spins polarized in-plane and deflected up and down resulting from a flow of charge current. [0007] Fig. 4A illustrates a plot showing write energy-delay conditions for one transistor and one MTJ with spin Hall effect (SHE) material compared to traditional MTJs.

[0008] Fig. 4B illustrates a plot comparing reliable write times for spin Hall MRAM and spin torque MRAM.

[0009] Figs. 5A-B illustrate three dimensional (3D) views of a device having an MTJ with magnets having perpendicular magnetizations and a stack without a SAF, according to some embodiments of the disclosure.

[0010] Figs. 6A-B illustrate 3D views of a device having an MTJ with magnets having in-plane magnetizations and a stack without the SAF, according to some embodiments of the disclosure.

[0011] Fig. 7 illustrates a cross-section of the MTJ stack of Fig. 5A without the SAF and with a composite fixed magnet under an interconnect (e.g., SOC interconnect), according to some embodiments of the disclosure.

[0012] Fig. 8 illustrates a plot showing micro-magnetic simulation of a SAF-less

MTJ, according to some embodiments of the disclosure.

[0013] Fig. 9A illustrates a plot showing spin polarization capturing switching of the composite magnet, according to some embodiments of the disclosure.

[0014] Fig. 9B illustrates a magnetization plot associated with Fig. 9A, according to some embodiments of the disclosure.

[0015] Fig. 9C illustrates a plot showing spin polarization capturing switching of a composite magnet using traditional spin orbit material, according to some embodiments of the disclosure.

[0016] Fig. 9D illustrates a magnetization plot associated with Fig. 9C, according to some embodiments of the disclosure.

[0017] Fig. 10 illustrates a cross-section of a die layout having the device of Fig. 5A formed in metal 3 (M3) and metal 2 (M2) layer regions, according to some embodiments of the disclosure.

[0018] Fig. 11 illustrates a cross-section of a die layout having the device of Fig. 5A formed in metal 2 (M2) and metal 1 (Ml) layer regions, according to some embodiments of the disclosure.

[0019] Fig. 12 illustrates a plot showing an improvement in energy-delay product using the device of Fig. 5A compared to the device of Fig. 2, in accordance with some embodiments of the disclosure. [0020] Fig. 13 illustrates a flowchart of a method of forming a SAF-less magnetic junction based memory with SOC, according to some embodiments of the disclosure.

[0021] Fig. 14 illustrates a smart device or a computer system or a SoC (System-on-

Chip) with a SAF-less magnetic junction, according to some embodiments of the disclosure.

DETAILED DESCRIPTION

[0022] SAF reduces asymmetry of a free magnet structure of a magnetic junction.

This asymmetry may be due to stray fields in the MTJs. Here, the asymmetry of the free magnet generally refers to the asymmetry in the hysteresis loop of the free magnet with reference to zero magnetic field point. In the absence of a SAF in a magnetic junction, dipolar interaction between the free magnet and the fixed magnet results in a highly asymmetrical reversal of the magnetization of the free magnet with respect to an applied field or to a current density. If the induced shift in the hysteresis loop is greater than a coercive field of the free magnet, then only one resistance state of the free magnet remains stable at zero field. Such a limitation is unsuitable for using magnetic junctions without something more. One way to reduce this asymmetry is to replace the fixed magnet with a SAF which consists of two ferromagnets that are anti-ferromagnetically coupled through a nonmagnetic spacer structure (e.g., Ru, Os, Hs, etc.). By selecting the correct thickness of the spacer structure, stray fields are reduced which in turn reduce the shift of the hysteresis loop of the free magnet. However, fabricating the SAF comes with its own challenges. For example, SAF may require high quality atomic crystallinity for its formation, may require a precise thickness to exhibit its behavior, and may demand low level of roughness for its fabrication.

[0023] Some embodiments describe a SAF-less perpendicular magnet switch which can be applied in logic and memory. In some embodiments, a magnetic junction is provided which includes a first structure (e.g., free magnet layer) comprising a magnet with smaller perpendicular magnetic anisotropy (PMA), wherein the first structure has an anisotropy axis perpendicular to a plane of a device; a second structure comprising one of a dielectric (e.g., MgO) or metal, the second structure being adjacent to the first structure; a third structure (e.g., a fixed magnet) comprising a magnet with larger PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures; and an interconnect (e.g., spin orbit coupling (SOC) interconnect or spin transfer torque (STT) interconnect) adjacent to the magnetic junction; and a fourth structure comprising a magnet with larger PMA, wherein the fourth structure is adjacent to the interconnect, and wherein the fourth structure has a magnetization which is opposite to a magnetization of the third structure. In various embodiments, the fourth structure provides the technical effect of the SAF without the challenges of fabricating the SAF. In some embodiments, the second structure comprises a metal or a metal oxide (e.g., AlO) that replaces the dielectric (e.g., MgO).

[0024] The term“free” or“unfixed” here with reference to a magnet refers to a magnet whose magnetization direction can change along its easy axis upon application of an external field or force (e.g., Oersted field, spin torque, etc.). Conversely, the term“fixed” or “pinned” here with reference to a magnet refers to a magnet whose magnetization direction is pinned or fixed along an axis and which may not change due to application of an external field (e.g., electrical field, Oersted field, spin torque,).

[0025] Here, perpendicularly magnetized magnet (or perpendicular magnet, or magnet with perpendicular magnetic anisotropy (PMA)) refers to a magnet having a magnetization which is substantially perpendicular to a plane of the magnet or a device. For example, a magnet with a magnetization which is in a z-direction in a range of 90 (or 270) degrees +/- 20 degrees relative to an x-y plane of a device.

[0026] Here, an in-plane magnet refers to a magnet that has magnetization in a direction substantially along the plane of the magnet. For example, a magnet with a magnetization which is in an x or y direction and is in a range of 0 (or 180 degrees) +/- 20 degrees relative to an x-y plane of a device.

[0027] The term“device” may generally refer to an apparatus according to the context of the usage of that term. For example, a device may refer to a stack of layers or structures, a single structure or layer, a connection of various structures having active and/or passive elements, etc. Generally a device is a three dimensional structure with a plane along the x-y direction and a height along the z direction of an x-y-z Cartesian coordinate system. The plane of the device may also be the plane of an apparatus which comprises the device.

[0028] In some embodiments, the additional fixed magnet adjacent to the SOC interconnect comprises a composite stack (e.g., alternate layers of Co and Pt) that can be optimized to decrease damping and coercivity of the primary free structure of the magnetic junction, which is switched by the SOC write electrode. In some embodiments, the fixed magnet or fixed structure of the magnetic junction is a perpendicular magnet and also comprises a composite stack (e.g., alternate layers of Co and Pt).

[0029] There are many technical effects of the various embodiments. For example, in some embodiments, the out-of-plane magnetization switching enables perpendicular magnet anisotropy (PMA) based magnetic devices (e.g., MRAM and logic) comprising spin orbit effects that generate perpendicular spin currents. The perpendicular magnet switch of some embodiments enables low programming voltages (or higher current for identical voltages) enabled by giant spin orbit effects (GSOE) for perpendicular magnetic memory and logic.

The perpendicular magnet switch, of some embodiments, results in lower write error rates which enable faster MRAM (e.g., write time of less than 10 ns). The perpendicular magnet switch of some embodiments decouple write and read paths to enable faster read latencies. The perpendicular magnet switch of some embodiments uses significantly smaller read current through the magnetic junction (e.g., MTJ or spin valve) and provides improved reliability of the tunneling oxide and MTJs. For example, less than 10 mA compared to 100 pA for nominal write is used by the perpendicular magnet switch of some embodiments. Further, by eliminating the use of a SAF in the magnetic junction, shift in the hysteresis loop of the free magnet of the junction is greatly reduced by introduction of an additional fixed magnet under the SOC interconnect. As such, the challenge of fabricating the SAF is mitigated.

[0030] In the following description, numerous details are discussed to provide a more thorough explanation of embodiments of the present disclosure. It will be apparent, however, to one skilled in the art, that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring embodiments of the present disclosure.

[0031] Note that in the corresponding drawings of the embodiments, signals are represented with lines. Some lines may be thicker, to indicate more constituent signal paths, and/or have arrows at one or more ends, to indicate primary information flow direction. Such indications are not intended to be limiting. Rather, the lines are used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit or a logical unit. Any represented signal, as dictated by design needs or preferences, may actually comprise one or more signals that may travel in either direction and may be implemented with any suitable type of signal scheme.

[0032] Throughout the specification, and in the claims, the term "connected" means a direct connection, such as electrical, mechanical, or magnetic connection between the things that are connected, without any intermediary devices. [0033] The term "coupled" means a direct or indirect connection, such as a direct electrical, mechanical, or magnetic connection between the things that are connected or an indirect connection, through one or more passive or active intermediary devices.

[0034] The term“adjacent” here generally refers to a position of a thing being next to

(e.g., immediately next to or close to with one or more things between them) or adjoining another thing (e.g., abutting it).

[0035] The term "circuit" or“module” may refer to one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function.

[0036] The term "signal" may refer to at least one current signal, voltage signal, magnetic signal, or data/clock signal. The meaning of "a," "an," and "the" include plural references. The meaning of "in" includes "in" and "on."

[0037] The term“scaling” generally refers to converting a design (schematic and layout) from one process technology to another process technology and subsequently being reduced in layout area. The term“scaling” generally also refers to downsizing layout and devices within the same technology node. The term“scaling” may also refer to adjusting (e.g., slowing down or speeding up - i.e. scaling down, or scaling up respectively) of a signal frequency relative to another parameter, for example, power supply level. The terms “substantially,”“close,”“approximately,”“near, ” and“about,” generally refer to being within +/- 10% of a target value.

[0038] Unless otherwise specified the use of the ordinal adjectives“first,”“second,” and“third,” etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner.

[0039] For the purposes of the present disclosure, phrases“A and/or B” and“A or B” mean (A), (B), or (A and B). For the purposes of the present disclosure, the phrase“A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0040] The terms“left,”“right,”“front,”“back,”“top,� �“bottom,”“over,”“under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions.

[0041] For the purposes of present disclosure, the terms“spin” and“magnetic moment” are used equivalently. More rigorously, the direction of the spin is opposite to that of the magnetic moment, and the charge of the particle is negative (such as in the case of electron). [0042] It is pointed out that those elements of the figures having the same reference numbers (or names) as the elements of any other figure can operate or function in any manner similar to that described, but are not limited to such.

[0043] Fig. 1A illustrates a magnetization hysteresis plot 100 for ferromagnet (FM)

101. The plot shows magnetization response to an applied magnetic field for ferromagnet 101. The x-axis of plot 100 is magnetic field Ή’ while the y-axis is magnetization‘m\ For FM 101, the relationship between Ή’ and‘m’ is not linear and results in a hysteresis loop as shown by curves 102 and 103. The maximum and minimum magnetic field regions of the hysteresis loop correspond to saturated magnetization configurations 104 and 106, respectively. In saturated magnetization configurations 104 and 106, FM 101 has stable magnetizations. In the zero magnetic field region 105 of the hysteresis loop, FM 101 does not have a definite value of magnetization, but rather depends on the history of applied magnetic fields. For example, the magnetization of FM 101 in configuration 105 can be either in the +x direction or the -x direction for an in-plane FM. As such, changing or switching the state of FM 101 from one magnetization direction (e.g., configuration 104) to another magnetization direction (e.g., configuration 106) is time consuming resulting in slower nanomagnets response time. It is associated with the intrinsic energy of switching proportional to the area in the graph contained between curves 102 and 103.

[0044] Fig. IB illustrates magnetization plot 120 for paramagnet 121. Plot 120 shows the magnetization response to an applied magnetic field for paramagnet 121. The x-axis of plot 120 is magnetic field Ή’ while the y-axis is magnetization‘m’. A paramagnet, as opposed to a ferromagnet, exhibits magnetization when a magnetic field is applied to it. Paramagnets generally have magnetic permeability greater or equal to one and hence are attracted to magnetic fields. Compared to plot 100, the magnetic plot 120 of Fig. IB does not exhibit hysteresis which allows for faster switching speeds and smaller switching energies between the two saturated magnetization configurations 124 and 126 of curve 122. In the middle region 125, paramagnet 121 does not have any magnetization because there is no applied magnetic field (e.g., H=0). The intrinsic energy associated with switching is absent in this case.

[0045] In some embodiments, paramagnet 121 comprises a material which includes one or more of: Platinum(Pt), Palladium (Pd), Tungsten (W), Cerium (Ce), Aluminum (Al), Lithium (Li), Magnesium (Mg), Sodium (Na), CnCh (chromium oxide), CoO (cobalt oxide), Dysprosium (Dy), Dy ₂ 0 (dysprosium oxide), Erbium (Er), EnCh (Erbium oxide), Europium (Eu), EU2O3 (Europium oxide), Gadolinium (Gd), Gadolinium oxide (Gd ₂ C)3). FeO and Fe ₂ 03 (Iron oxide), Neodymium (Nd), Nd ₂ 03 (Neodymium oxide), KO2 (potassium superoxide), praseodymium (Pr), Samarium (Sm), SrruCb (samarium oxide), Terbium (Tb), Tb ₂ 03 (Terbium oxide), Thulium (Tm), TrmCb (Thulium oxide), or V ₂ 03 (Vanadium oxide). In some embodiments, paramagnet 121 comprises dopants which include one or more of: Ce,

Cr, Mn, Nb, Mo, Tc, Re, Nd, Gd, Tb, Dy, Ho, Er, Tm, or Yb. In various embodiments, the magnet can be either a FM or a paramagnet.

[0046] Fig. 2 illustrates device 200 having an out-of-plane magnetic junction stack coupled to a spin orbit coupling interconnect, where the magnetic junction stack includes a synthetic anti-ferromagnet (SAF). Here, the stack of structures having magnetic junction 221 is coupled to an electrode 222 comprising spin Hall effect (SHE) or SOC material, where the SHE material converts charge current Iw (or write current) to spin polarized current Is.

Device 200 forms a three terminal memory cell with SHE induced write mechanism and MTJ based read-out. Device 200 comprises magnetic junction 221, SHE Interconnect or electrode 222, and non-magnetic metal(s) 223a/b. In one example, MTJ 221 comprises structures 22la, 22lb, and 22lc. In some embodiments, structures 22la and 22lc are ferromagnetic structures. In some embodiments, structure 22 lb is a metal or a tunneling dielectric.

[0047] For example, when the magnetic junction is a spin valve, structure 22lb is metal or a metal oxide (e.g., a non-magnetic metal such as Al and/or its oxide) and when the magnetic junction is a tunneling junction, then structure 22 lb is a dielectric (e.g. MgO). One or both ends along the horizontal direction of SHE Interconnect 222 is formed of non magnetic metals 223 a/b. Additional structures 22 ld, 22 le, 22 lf, and 22 lg can also be stacked on top of structure 22lc. In some embodiments, structure 22lg is a non-magnetic metal electrode. Here, the thickness of layer 22lc is denoted as I)i. of layer 22ld as t, and of layer 22 le as D2.

[0048] So as not to obscure the various embodiments, the magnetic junction is described as a magnetic tunneling junction (MTJ). However, the embodiments are also applicable for spin valves. A wide combination of materials can be used for material stacking of magnetic j unction 221. For example, the stack of structures 22 la, 22 lb, 22 lc, 22 ld, 22 le, 22lf, and 22lg are formed of materials which include: Co _x Fe _y B _z , MgO, Co _x Fe _y B _z , Ru, Co _x Fe _y B _z , IrMn, and Ru, respectively, where‘x,’‘y,’ and‘z’ are fractions of elements in the alloys. Other materials may also be used to form MTJ 221. MTJ 221 stack comprises free magnetic structure 22la, MgO tunneling oxide 22lb, a fixed magnetic structure 22lc/d/e which is a combination of CoFe, Ru, and CoFe structures, respectively, referred to as Synthetic Anti-Ferromagnet (SAF), and an Anti-Ferromagnet (AFM) structure 22 lf. The SAF structure has the property, that the magnetizations in the two CoFe structures are opposite, and allows for cancelling the dipole fields around the free magnetic structure such that a stray dipole field will not control the free magnetic structure.

[0049] In some embodiments, the free and fixed magnetic structures (221 a and 221 c, respectively) are formed of CFGG (i.e., Cobalt (Co), Iron (Fe), Germanium (Ge), or Gallium (Ga) or a combination of them). In some embodiments, FM 22la/c are formed from Heusler alloys. Heusler alloys are ferromagnetic metal alloys based on a Heusler phase. Heusler phases are intermetallic with certain composition and face-centered cubic crystal structure. The ferromagnetic property of the Heusler alloys are a result of a double-exchange mechanism between neighboring magnetic ions. In some embodiments, the Heusler alloy includes one of: Cu ₂ MnAl, Cu ₂ MnIn, Cu ₂ MnSn, Ni ₂ MnAl, Ni ₂ MnIn, Ni ₂ MnSn, Ni ₂ MnSb, Ni ₂ MnGa Co ₂ MnAl, Co ₂ MnSi, Co ₂ MnGa, Co ₂ MnGe, Pd ₂ MnAl, Pd ₂ MnIn, Pd ₂ MnSn, Pd ₂ MnSb, Co ₂ FeSi, Co ₂ FeAl, Fe ₂ VAl, Mn ₂ VGa, Co ₂ FeGe, MnGa, or MnGaRu.

[0050] In some embodiments, fixed magnet structure 22 lc is a magnet with perpendicular magnetic anisotropy (PMA). For example, fixed magnet structure 22lc has a magnetization pointing along the z-direction and is perpendicular to the x-y plane of the device 200. In some embodiments, the magnet with PMA comprises a stack of materials, wherein the materials for the stack are selected from a group consisting of: Co and Pt; Co and Pd; Co and Ni; MgO, CoFeB, Ta, CoFeB, and MgO; MgO, CoFeB, W, CoFeB, and MgO; MgO, CoFeB, V, CoFeB, and MgO; MgO, CoFeB, Mo, CoFeB, and MgO; Mn _x Ga _y ;

Materials with Llo symmetry; and materials with tetragonal crystal structure. In some embodiments, the magnet with PMA is formed of a single structure of one or more materials. In some embodiments, the single structure is formed of MnGa.

[0051] Llo is a crystallographic derivative structure of a FCC (face centered cubic lattice) structure and has two of the faces occupied by one type of atom and the comer and the other face occupied with the second type of atom. When phases with the Llo structure are ferromagnetic the magnetization vector usually is along the [0 0 1] axis of the crystal.

Examples of materials with Llo symmetry include CoPt and FePt. Examples of materials with tetragonal crystal structure and magnetic moment are Heusler alloys such as CoFeAl, MnGe, MnGeGa, and MnGa.

[0052] SHE Interconnect 222 (or the write electrode) includes 3D materials such as one or more of b-Tantalum (b-Ta), Ta, b-Tungsten (b-W), W, Pt, Copper (Cu) doped with elements such as Iridium, Bismuth and any of the elements of 3d, 4d, 5d and 4f, 5f periodic groups in the Periodic Table which may exhibit high spin orbit coupling. In some embodiments, SHE interconnect 222 comprises a spin orbit 2D material which includes one or more of: graphene, BiSe2, B1S2, BiSe _x Te2-x, T1S2, WS?., M0S2, TiSe2, WSe2, MoSe2, B2S3, Sb ₂ S ₃ , Ta ₂ S, Re ₂ S7, LaCPS ₂ , LaOAsS ₂ , ScOBiS ₂ , GaOBiS ₂ , AIOB1S2, LaOSbS ₂ , BiOBiS ₂ , YOB1S2, InOBiS ₂ , LaOBiSe ₂ , TiOBiS ₂ , CeOBiS ₂ , PrOBiS ₂ , NdOBiS ₂ , LaOBiS ₂ , or SrFBiS ₂ . In some embodiments, the SHE interconnect 222 comprises spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material such as WS2, WSe2, WTe2, M0S2, MoSe2, MoTe2, PtSe2, PS2, B2S3, Sb2S ₃ , and Ta ₂ S. In some embodiments, the SHE interconnect 222 comprises a spin orbit material which includes materials that exhibit Rashba-Bychkov effect. In some embodiments, material which includes materials that exhibit Rashba-Bychkov effect comprises materials ROCh2, where‘R’ includes one or more of: La, Ce, Pr, Nd, Sr, Sc, Ga, Al, or In, and where“Ch” is a chalcogenide which includes one or more of: S, Se, or Te.

[0053] In some embodiments, SHE Interconnect 222 transitions into high

conductivity non-magnetic metal(s) 223a/b to reduce the resistance of SHE Interconnect 222. The non-magnetic metal(s) 223a/b include one or more of: Cu, Co, a-Ta, Al, CuSi, or NiSi.

[0054] In one case, the magnetization direction of fixed magnetic structure 22lc is perpendicular relative to the magnetization direction of free magnetic structure 22 la (e.g., magnetization directions of the free and fixed magnetic structures are not parallel, rather they are orthogonal). For example, the magnetization direction of free magnetic structure 22 la is in-plane while the magnetization direction of fixed magnetic structure 22 lc is perpendicular to the in-plane. In another case, magnetization direction of fixed magnetic structure 22 la is in-plane while the magnetization direction of free magnetic structure 221 c is perpendicular to the plane.

[0055] The thickness of a ferromagnetic structure (e.g., fixed or free magnetic layer) may determine its equilibrium magnetization direction. For example, when the thickness of the ferromagnetic structure 22la/c is above a certain threshold (depending on the material of the magnet, e.g. approximately 1.5 nm for CoFe), then the ferromagnetic structure exhibits magnetization direction which is in-plane. Likewise, when the thickness of the ferromagnetic structure 22la/c is below a certain threshold (depending on the material of the magnet), then the ferromagnetic structure 22la/c exhibits magnetization direction which is perpendicular to the plane of the magnetic structure.

[0056] Other factors may also determine the direction of magnetization. For example, factors such as surface anisotropy (depending on the adjacent structures or a multi- structure composition of the ferromagnetic structure) and/or crystalline anisotropy

(depending on stress and the crystal lattice structure modification such as FCC (face centered cubic lattice), BCC (body centered cubic lattice), or Llo-type of crystals, where Llo is a type of crystal class which exhibits perpendicular magnetizations), can also determine the direction of magnetization.

[0057] In this example, the applied current I _w is converted into spin current by SHE

Interconnect 222 (also referred to as the spin orbit coupling interconnect). This spin current switches the direction of magnetization of the free structure and thus changes the resistance of MTJ 221. However, to read out the state of MTJ 221, a sensing mechanism is needed to sense the resistance change.

[0058] The magnetic cell is written by applying a charge current via SHE

Interconnect 222. The direction of the magnetic writing in free magnet structure 22 la is decided by the direction of the applied charge current. Positive currents (e.g., currents flowing in the +y direction) produce a spin injection current with transport direction (along the +z direction) and spins pointing to the +x direction. The injected spin current in turn produces spin torque to align the free magnet 221 a (coupled to the SHE structure 222 of SHE material) in the +x direction. Negative currents (e.g., currents flowing in the -y direction) produce a spin injection current with transport direction (along the +z direction) and spins pointing to the -x direction. The injected spin current in turn produces spin torque to align the free magnet 22 la (coupled to the SHE material of structure 222) in the -x direction. In some embodiments, in materials with the opposite sign of the SHE/SOC effect, the directions of spin polarization and thus of the free structure magnetization alignment are reversed compared to the above.

[0059] Fig. 3 illustrates a cross-section 300 of the spin orbit coupling interconnect with electrons having their spins polarized in-plane and deflected up and down resulting from a flow of charge current. In this example, positive charge current represented by J _c produces spin-front (e.g., in the +x direction) polarized current 301 and spin-back (e.g., in the -x direction) polarized current 302. The injected spin current l _s generated by a charge current I _c in the write electrode 222 is given by:

where, the vector of spin current I _s = I _f — / _j, points in the direction of transferred magnetic moment and has the magnitude of the difference of currents with spin along and opposite to the spin polarization direction, z is the unit vector perpendicular to the interface, P _S HE is the spin Hall injection efficiency which is the ratio of magnitude of transverse spin current to lateral charge current, w is the width of the magnet, t is the thickness of the SHE

Interconnect (or write electrode) 222, _S f is the spin flip length in SHE Interconnect 222,

Q _5HE is the spin Hall angle for SHE Interconnect 222 to free ferromagnetic structure interface. The injected spin angular momentum responsible for the spin torque given by:

S = h T _s /2e . . . (2)

[0060] The generated spin up and down currents 301/302 (e.g., / _s ) are described as a vector cross-product given by:

[0061] This spin to charge conversion is based on Tunnel Magneto Resistance (TMR) which is highly limited in the signal strength generated. The TMR based spin to charge conversion has low efficiency (e.g., less than one).

[0062] Fig. 4A illustrates plot 420 showing write energy-delay conditions for one transistor and one magnetic tunnel junction (MTJ) with spin Hall effect (SHE) material compared to traditional MTJs. Here, x-axis is energy per write operation in femto-Joules (fJ) while the y-axis is delay in nanoseconds (ns).

[0063] Here, the energy-delay trajectory of SHE and MTJ devices are compared for in-plane magnet switching as the applied write voltage is varied. The energy-delay relationship (for in-plane switching) can be written as:

where R _write is the write resistance of the device (resistance of SHE electrode or resistance of MTJ-P or MTJ-AP, where MTJ-P is a MTJ with parallel magnetizations while MTJ-AP is an MTJ with anti-parallel magnetizations, m ₀ is vacuum permeability, e is the electron charge. The equation shows that the energy at a given delay is directly proportional to the square of

M Ve

the Gilbert damping a. Here the characteristic time, t ₀ = ^s / _j ^varies as the spin polarization varies for various SHE metal electrodes (e.g., 423, 424, 425). Plot 420 shows five curves 421, 422, 423, 424, and 425. Curves 421 and 422 show write energy-delay conditions using traditional MTJ devices without SHE material.

[0064] For example, curve 421 shows the write energy-delay condition caused by switching a magnet from anti-parallel (AP) to parallel (P) state, while curve 422 shows the write energy-delay condition caused by switching a magnet from P to AP state. Curves 422, 423, and 424 show write energy-delay conditions of an MTJ with SHE material. Clearly, write energy-delay conditions of an MTJ with SHE material is much lower than the write energy-delay conditions of an MTJ without SHE material. While the write energy-delay of an MTJ with SHE material improves over a traditional MTJ without SHE material, further improvement in write energy-delay is desired.

[0065] Fig. 4B illustrates plot 430 comparing reliable write times for spin Hall

MRAM and spin torque MRAM. There are three cases considered in plot 430. Waveform 431 is the write time for in-plane MTJ, waveform 432 is the write time for PMA MTJ, and waveform 434 is the write time for spin Hall MTJ. The cases considered here assume a 30 X 60 nm magnet with 40 kT energy barrier and 3.5 nm SHE electrode thicknesses. The energy- delay trajectories of the devices are obtained assuming a voltage sweep from 0 V to 0.7 V in accordance to voltage restrictions of scaled CMOS. The energy-delay trajectory of the SHE- MTJ devices exhibits broadly two operating regions A) Region 1 where the energy-delay

M Ve

product is approximately constant (z _d < ^s // ¾ and Region 2 where the energy is

M Ve

proportional to the delay t _a > ^s / _j p The two regions are separated by energy

minima at where minimum switching energy is obtained for the spin

torque devices.

[0066] The energy-delay trajectory of the STT-MTJ (spin transfer torque MTJ) devices is limited with a minimum delay of 1 ns for in-plane devices at 0.7 V maximum applied voltage, the switching energy for P-AP and AP-P are in the range of 1 pJ/write. In contrast, the energy-delay trajectory of SHE-MTJ (in-plane anisotropy) devices can enable switching times as low as 20 ps (b-W with 0.7 V, 20 fj/bit) or switching energy as small as 2 fj (b-W with 0.1 V, 1.5 ns switching time).

[0067] Figs. 5A-B illustrate three dimensional (3D) views, 500 and 520, respectively, of a device having an MTJ with magnets having perpendicular magnetizations and a stack without SAF, according to some embodiments of the disclosure. The traditional use of SAF 221 d/e is an anti-ferromagnet to cancel the dipole field around the free magnetic structure 22 la such that a stray dipole field will not control the free magnetic structure 22 la. However designing and fabricating SAF 221 d/e is complex.

[0068] A typical SAF comprises fixed magnets with an exchange structure (or spacer layer) between them. The exchange structure can include one or more of: Ru, Ir, Al, Cu, or Ag. For SAF to cancel the dipole field, the thickness of the exchange structure is carefully designed so there is spin tunneling through it. Any un-cancelled dipole field can interfere with the magnetization of free magnet 22 la resulting in higher write current and write error rates. Fabricating the SAF may also use high atomic crystallinity between the fixed magnets and the exchange structure between them. In various embodiments, SAF 221 d/e is removed, and the technical effect of SAF 221 d/e is provided by fabricating an additional fixed magnet 501 under electrode 122 such that the free magnet 22la is adjacent to one surface (e.g., the top surface) of interconnect 122 while the additional fixed magnet 501 is formed on the other surface (e.g., the bottom surface) of interconnect 122.

[0069] In various embodiments, the magnetization of the additional fixed magnet 501 is opposite to the magnetization of the fixed magnet 22 lc of the magnetic junction. As such, fixed magnet 501 cancels the dipole field from fixed structure 22lc. For example, magnetization 502 of fixed magnet 501 is opposite to magnetization 503 of fixed magnet 22lc. In this example, magnetization 503 points in the +z direction while magnetization 502 points in the -z direction. Fig. 5B is similar to Fig. 5A except for different magnetization of the fixed magnet 22 lc and corresponding fixed magnet 522. In this example, magnetization 523 points in the -z direction while magnetization 522 points in the +z direction. Here, the thickness of layer 502 is designated as D2. The range of this thickness is designed such that its dipole field approximately compensates the dipole field produced by layer 22 lc.

Additionally, these two layers (e.g., fixed magnets) have different coercive fields and their magnetizations can be set consecutively by applying an external magnetic field in a positive and then in negative direction along the z-axis.

[0070] While the various embodiments illustrate the use of fixed magnet 501 being adjacent to a spin Hall effect write electrode 222, the embodiments are applicable to a regular spin transfer torque electrode (not shown) which can replace spin Hall effect write electrode 222

[0071] In some embodiments, the additional fixed magnet 501 comprises a stack of structures (also referred to as a composite stack) as opposed to a single structure. In some embodiments, the stack of structures of the additional fixed magnet 501 comprises alternating structures of a first material and a second material. In some embodiments, the first material includes one of: Co, Ni, Fe, or Heusler alloy. In some embodiments, the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the composite stack is formed with a sufficiently high anisotropy (indicated by an effective anisotropy magnetic field Hk) and sufficiently low saturated magnetization (M _s ) to increase injection of spin currents. Saturated magnetization M _s is generally the state reached when an increase in applied external magnetic field H cannot increase the magnetization of the material. Here, sufficiently low Ms refers to Ms less than 200 kA/m (kilo-Amperes per meter). Anisotropy Hk generally refers to the material property which is directionally dependent. Materials with high Hk are materials with material properties that are highly directionally dependent. Here, sufficiently high Hk in context of Heusler alloys is considered to be greater than 2000 Oe (Oersted).

[0072] Figs. 6A-B illustrate 3D views, 600 and 620, respectively, of a device having an MTJ with magnets having in-plane magnetizations and a stack without SAF, according to some embodiments of the disclosure. Compared to the devices of Figs. 5A-B, here the magnetizations of the free structure 62 la, fixed structure 62 lc, and additional fixed structure are in-plane. For example, the magnetization directions are along the plane of the device. Material wise, free and fixed magnet structures 62la, 62lc, and 601/622 can be same as materials for free and fixed magnet structures 22la, 22lc, and 501, respectively. In some embodiments, the thickness of the free and fixed magnet structures 62la, 62lc, and 601/622 are adjusted relative to the free and fixed magnet structures 22la, 22lc, and 501 to change the anisotropy from perpendicular to in-plane.

[0073] In various embodiments, the magnetization of the additional fixed magnet 601 is opposite to the magnetization of fixed magnet 62 lc of the magnetic junction. As such, fixed magnet 601 cancels the dipole field around the free magnetic structure 621 a such that a stray dipole field will not control the free magnetic structure 62 la. For example, magnetization 602 of magnet 601 is opposite to magnetization 603 of magnet 62lc. In this example, magnetization 603 points in the -y direction while magnetization 602 points in the +y direction. Fig. 6B is similar to Fig. 6A except for the different magnetizations of the fixed magnet 62 lc and corresponding additional fixed magnet 622. In this example, magnetization 623 points in the +y direction while magnetization 622 points in the -y direction. In some embodiments, fixed magnet(s) 501/521/601/621 are a ferromagnet, paramagnet, or a combination of both.

[0074] Fig. 7 illustrates cross-section 700 of the MTJ stack of Fig. 5A without SAF and with a composite fixed magnet under an SOC interconnect, according to some embodiments of the disclosure. In some embodiments, fixed magnet 701 (e.g., 501 and 521) is a composite structure (or a multi-structure fixed magnet) comprising alternating structures of 703 and 704. This multi-structure fixed (or pinned) magnet 701 replaces the single structure free magnet 501/521 of Fig. 5, in accordance with some embodiments. This multi structure fixed magnet 701 is also referred to as a composite magnet formed of a composite stack of material. For example, the composite stack comprises structures 703 i _-n and 704i _-n are stacked in an alternating manner, where‘n’ has a range of 1 to 10. In some embodiments, the composite stack 701 comprises alternating structures of a first material and a second material. In some embodiments, the first material includes one of: Co, Ni, Fe, or Heusler alloy. In some embodiments, the second material includes one of: Pt, Pd, Ir, Ru, or Ni.

[0075] In some embodiments, the first material includes one of: Co, Ni, Fe, or

Heusler alloy. In some embodiments, the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V. In some embodiments, the Heusler alloy includes one of: Cu ₂ MnAl, CmMnln. CmMnSn. Ni ₂ MnAl, Ni ₂ MnIn, Ni ₂ MnSn, Ni ₂ MnSb, Ni ₂ MnGa Co ₂ MnAl, Co ₂ MnSi, Co ₂ MnGa, Co ₂ MnGe, Pd ₂ MnAl, Pd ₂ MnIn, Pd ₂ MnSn, Pd ₂ MnSb, Co ₂ FeSi, Co ₂ FeAl, Fe ₂ VAl, Mn ₂ VGa, Co ₂ FeGe, MnGa, or MnGaRu. In some embodiments, the first material has a thickness tl in a range of 0.6 nm to 2 nm. In some embodiments, the second material has a thickness t2 in a range of 0.1 nm to 3 nm.

[0076] While the embodiments here show the first material being at the bottom followed by the second material, the order can be reversed without changing the technical effect. In some embodiments, the thickness of fixed magnet (or pinned magnet) 701 is from 2 nm to 15 nm, the thickness of interconnect 222 is from 3 nm to 20 nm, the thickness of free magnet 22la is from 0.5 nm to 5 nm, thickness of dielectric structure 22lb is from 0.5 nm to 5 nm, and the thickness of fixed magnet 22 lc is from 2nm to 15 nm.

[0077] While the embodiment of Fig. 7 illustrates fixed magnets 501/521 being composite magnets, the same concept can also be applied to in-plane fixed magnets 601/621. Further, the fixed magnets of the magnetic junctions (in-plane or perpendicular) can also be formed using composite magnet structures in accordance with some embodiments.

[0078] Fig. 8 illustrates plot 800 showing a micro-magnetic simulation of the SAF- less MTJ (e.g., device of Figs. 5A-B), according to some embodiments of the disclosure. Here, x-axis is magnetic field strength in mill Tesla (mT), and the y-axis is magnetization between 0 and 1. The simulation parameters are: the magnetization of the free layer which in this example is Mf=800 kA/m, the magnetization in the fixed layers which in this example is Mr=800 kA/m, anisotropy energy with the easy axis along the z-direction for the bottom fixed layer which is Kb=l2*l0 ⁵ Pa, of the free layer is Kf=5.3*l0 ⁵ Pa, Kr=8*l0 ⁵ Pa, thicknesses tpl=9 nm, t3=6, tf=l nm, t4=l nm, and tp2=6 nm, and the diameter of the magnetic pillar is d=50 nm. [0079] In various embodiments, fixed magnet 701 cancels the dipole effect on free magnet 22la so that the hysteresis loops of the free magnet 22la are centered. As such, the asymmetry in the hysteresis loops of free magnet 22 la is reduced or eliminated. In some embodiments, by selecting the correct thickness t3 of interconnect 222 and dielectric t4 22 lb, the dipole field exerted on free magnet 22 la is equal in magnitude but opposite in direction than the dipole field of fixed magnet 701. Here, three hysteresis loops (e.g., magnetization projection along the z-axis in a layer relative to its total magnetization vs. an external magnetic field H applied along z-axis) are shown for the bottom fixed layer 801, for the top fixed layer 802, and for the free layer 803 with hysteresis. The hysteresis loops demonstrate that 801 and 802 have different values of the coercive field (e.g., the field value at which magnetization switches). Hysteresis 803 is centered, which shows that the net dipole field acting on the free layer vanishes.

[0080] Fig. 9A illustrates a plot 900 showing spin polarization capturing switching of magnet 22 la, according to some embodiments of the disclosure. Fig. 9B illustrates a magnetization plot 920 associated with Fig. 9A, according to some embodiments of the disclosure.

[0081] Plot 900 shows switching of the spin orbit torque device with PMA. Here, waveforms 901, 902, and 902 represent the magnetization projections on the x, y, and z axes, respectively. The magnet starts with z-magnetization of -1. Positive spin orbit torque (SOT) is applied from 5 to 50 ns (nanoseconds). It leads to switching the z-magnetization to 1.

Then, a negative spin orbit torque is applied between 120 and 160 ns. It leads to switching the z-magnetization to 1. This illustrates change of magnetization in response to write charge current of certain polarity.

[0082] Fig. 9C illustrates a plot 930 showing the spin polarization capturing switching of magnet 22 la using a traditional spin orbit material, according to some embodiments of the disclosure. Fig. 9D illustrates a magnetization plot 940 associated with Fig. 9C, according to some embodiments of the disclosure. Here, waveforms 931, 932, and 932 represent the magnetization projections on x, y, and z axes, respectively. The difference from the case of Fig. 9C is that negative spin orbit torque (SOT) is applied from 5 to 50 ns. As a result, the z-magnetization remains close to -1. This illustrates the persistence of magnetization in response to write charge current of opposite polarity.

[0083] Fig. 10 illustrates a cross-section 1000 of a die layout having the device of

Fig. 5A formed in metal 3 (M3) and metal 2 (M2) structure regions, according to some embodiments of the disclosure. Cross-section 1000 illustrates an active region having a transistor MN comprising diffusion region 1001, a gate terminal 1002, drain terminal 1004, and source terminal 1003. The source terminal 1003 is coupled to SL (source line) via poly or via, where the SL is formed on Metal 0 (M0). In some embodiments, the drain terminal 1004 is coupled to MOa (also metal 0) through via 1005. The drain terminal 1004 is coupled to spin Hall electrode 222/1022 through Via 0-1 (e.g., via connecting metal 0 to metal 1 structures), metal 1 (Ml), Via 1-2 (e.g., via connecting metal 1 to metal 2 structures), and Metal 2 (M2).

[0084] In some embodiments, the magnetic junction (e.g., MTJ 1021 or spin valve) is formed in the metal 3 (M3) region. Here, MTJ 1021 (or spin valve) can be according to any one of MTJs described with reference to Figs. 5-7. Referring back to Fig. 10, in some embodiments, the perpendicular free magnet structure of the magnetic junction (MTJ 1021 or spin valve) couples to spin Hall electrode 1022 (e.g., electrode 222), and further the spin Hall electrode 1022 is coupled to the additional fixed magnet 1023. The magnetic junction is SAF free, and the technical effect of the SAF is provided by the additional fixed magnet 1023 (e.g., 501/521/601/621), in accordance with various embodiments. In some embodiments, the fixed magnet structure of magnetic junction couples to the bit-line (BL) via spin Hall electrode 1022 through Via 3-4 (e.g., via connecting metal 4 region to metal 4 (M4)). In this example, the bit-line is formed on M4.

[0085] In some embodiments, an n-type transistor MN is formed in the frontend of the die while the spin Hall electrode 1022 and the fixed magnet 1023 are located in the backend of the die. Here, the term“backend” generally refers to a section of a die which is opposite of a“frontend” and where an IC (integrated circuit) package couples to IC die bumps. For example, high level metal structures (e.g., metal structure 6 and above in a ten metal stack die) and corresponding vias that are closer to a die package are considered part of the backend of the die. Conversely, the term“frontend” generally refers to a section of the die that includes the active region (e.g., where transistors are fabricated) and low level metal structures and corresponding vias that are closer to the active region (e.g., metal structure 5 and below in the ten metal stack die example). In some embodiments, the spin Hall electrode 1022 and the fixed magnet 1023 are located in the backend metal structures or via structures for example in Via 3. In some embodiments, the electrical connectivity to the device is obtained in structures M0 and M4 or Ml and M5 or any set of two parallel interconnects.

[0086] Fig. 11 illustrates a cross-section 1100 of a die layout having the device of

Fig. 5A formed in metal 2 (M2) and metal 1 (Ml) structure regions, according to some embodiments of the disclosure. Compared to Fig. 10, here the magnetic junction (e.g., MTJ 1021 or spin valve) is formed in the metal 2 region and/or Via 1-2 region. In some embodiments, the spin Hall electrode 1022 and the additional fixed magnet 1023 are formed in the metal 1 region.

[0087] Fig. 12 illustrates a plot 1200 showing improvement in energy-delay product using the device of Fig. 5A compared to the device of Fig. 2, in accordance with some embodiments of the disclosure. Here, the x-axis is Write Energy (in fj) and the y-axis is Delay (in ns). Here, two the energy-delay trajectories are compared as write voltage is varied— 1201 which is the energy-delay trajectory of device 200, and 1202 is the energy delay trajectory of device 500. Plot 1200 illustrates that device(s) 500/520/600/620 provide a shorter (i.e., improved) energy-delay product than device 200.

[0088] Fig. 13 illustrates a flowchart 1300 of a method of forming a SAF-less magnetic junction based memory with SOC, according to some embodiments of the disclosure. While the blocks (e.g., operations or processes) are illustrated in a specific order, the order of the blocks can be changed. For example, some blocks can be performed others, while others can be performed together with another block.

[0089] At block 301 a first structure is formed comprising a magnet with smaller perpendicular magnetic anisotropy (PMA), wherein the first structure has an anisotropy axis perpendicular to a plane of a device. At block 1302, a second structure is formed comprising one of a dielectric or metal, the second structure being adjacent to the first structure. At block 1303, a third structure is formed comprising a magnet with larger PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures. At block 1304, an interconnect is formed adjacent to the magnetic junction. At block 1305, a fourth structure is formed comprising a magnet with larger PMA, wherein the fourth structure is adjacent to the interconnect, wherein the fourth structure has a magnetization which is opposite to a magnetization of the third structure, wherein the first, second, and third structures are part of a magnetic junction.

[0090] In some embodiments, forming the interconnect comprises forming a material exhibiting spin orbit coupling. In some embodiments, the method of forming the fourth structure comprises forming a first material and a second material different from the first material, and wherein the first and second materials are in a stack. In some embodiments, the first material includes one of: Co, Ni, Fe, or Heusler alloy. In some embodiments, the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V. In some embodiments, the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the first material has a thickness in a range of 0.6 nm to 2 nm, and wherein the second material has a thickness in a range of 0.1 nm to 3 nm.

[0091] In some embodiments, the dielectric comprises: Mg and O. In some embodiments, the method of forming the fourth structure comprises forming a super lattice including a first material and a second material, wherein the first material includes one of:

Co, Ni, Fe, or Heusler alloy, and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the method of forming the fourth structure adjacent to the interconnect such that the magnetic junction is adjacent to a first surface of the interconnect, wherein the fourth structure is adjacent to a second surface of the interconnect, and wherein the second surface is opposite to the first surface. In some embodiments, the interconnect is to generate spin Hall effect (SHE). In some embodiments, the interconnect includes one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b-W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth, or elements of 3d, 4d, 5d and 4f, 5f periodic groups, graphene, Ti, S, W, Mo, Se, Sb, B, Re, La, C, P, O, As, Sc, Ga, Al, Y, In, Ce, Pr, Nd, Sr, or F. In some embodiments, the method of forming the interconnect comprises forming a spin orbit material which includes one of a 2D material or a 3D material, and wherein the 3D material is thinner than the 2D material. In some embodiments, the method of forming the interconnect comprises forming a spin orbit material which includes materials that exhibit Rashba-Bychkov effect. In some embodiments, the magnetic junction is one of a spin valve or a magnetic tunneling junction (MTJ).

[0092] In some embodiments, the magnet of the fourth structure is a paramagnet which includes one or more of: Pt, Pd, W, Ce, Al, Li, Mg, Na, Cr, Co, O, Dy, Er, Eu, Gd, Fe, Nd, K, Pr, Sm, Tb, Tm, or V. In some embodiments, the magnet of the fourth structure is a paramagnet which comprises dopants which include one or more of: Ce, Cr, Mn, Nb, Mo, Tc, Re, Nd, Gd, Tb, Dy, Ho, Er, Tm, or Yb.

[0093] Fig. 14 illustrates a smart device or a computer system or a SoC (System-on-

Chip) with a SAF-less magnetic junction, according to some embodiments of the disclosure.

[0094] For purposes of the embodiments, the transistors in various circuits and logic blocks described here are metal oxide semiconductor (MOS) transistors or their derivatives, where the MOS transistors include drain, source, gate, and bulk terminals. The transistors and/or the MOS transistor derivatives also include Tri-Gate and FinFET transistors, Gate All Around Cylindrical Transistors, Tunneling FET (TFET), Square Wire, or Rectangular Ribbon Transistors, ferroelectric FET (FeFETs), or other devices implementing transistor functionality like carbon nanotubes or spintronic devices. MOSFET symmetrical source and drain terminals i.e., are identical terminals and are interchangeably used here. A TFET device, on the other hand, has asymmetric Source and Drain terminals. Those skilled in the art will appreciate that other transistors, for example, Bi-polar junction transistors (BJT PNP/NPN), BiCMOS, CMOS, etc., may be used without departing from the scope of the disclosure.

[0095] Fig. 14 illustrates a block diagram of an embodiment of a mobile device in which flat surface interface connectors could be used. In some embodiments, computing device 1600 represents a mobile computing device, such as a computing tablet, a mobile phone or smart-phone, a wireless-enabled e-reader, or other wireless mobile device. It will be understood that certain components are shown generally, and not all components of such a device are shown in computing device 1600.

[0096] In some embodiments, computing device 1600 includes first processor 1610 with a SAF-less magnetic junction (e.g., any one of devices of Figs. 5-7), according to some embodiments discussed. Other blocks of the computing device 1600 may also include a magnetic junction having a SAF-less magnetic junction, according to some embodiments.

The various embodiments of the present disclosure may also comprise a network interface within 1670 such as a wireless interface so that a system embodiment may be incorporated into a wireless device, for example, cell phone or personal digital assistant.

[0097] In some embodiments, processor 1610 (and/or processor 1690) can include one or more physical devices, such as microprocessors, application processors,

microcontrollers, programmable logic devices, or other processing means. The processing operations performed by processor 1610 include the execution of an operating platform or operating system on which applications and/or device functions are executed. The processing operations include operations related to I/O (input/output) with a human user or with other devices, operations related to power management, and/or operations related to connecting the computing device 1600 to another device. The processing operations may also include operations related to audio I/O and/or display I/O.

[0098] In some embodiments, computing device 1600 includes audio subsystem

1620, which represents hardware (e.g., audio hardware and audio circuits) and software (e.g., drivers, codecs) components associated with providing audio functions to the computing device. Audio functions can include speaker and/or headphone output, as well as microphone input. Devices for such functions can be integrated into computing device 1600, or connected to the computing device 1600. In one embodiment, a user interacts with the computing device 1600 by providing audio commands that are received and processed by processor 1610.

[0099] In some embodiments, computing device 1600 comprises display subsystem

1630. Display subsystem 1630 represents hardware (e.g., display devices) and software (e.g., drivers) components that provide a visual and/or tactile display for a user to interact with the computing device 1600. Display subsystem 1630 includes display interface 1632, which includes the particular screen or hardware device used to provide a display to a user. In one embodiment, display interface 1632 includes logic separate from processor 1610 to perform at least some processing related to the display. In one embodiment, display subsystem 1630 includes a touch screen (or touch pad) device that provides both output and input to a user.

[00100] In some embodiments, computing device 1600 comprises I/O controller 1640. I/O controller 1640 represents hardware devices and software components related to interaction with a user. I/O controller 1640 is operable to manage hardware that is part of audio subsystem 1620 and/or display subsystem 1630. Additionally, I/O controller 1640 illustrates a connection point for additional devices that connect to computing device 1600 through which a user might interact with the system. For example, devices that can be attached to the computing device 1600 might include microphone devices, speaker or stereo systems, video systems or other display devices, keyboard or keypad devices, or other I/O devices for use with specific applications such as card readers or other devices.

[00101] As mentioned above, I/O controller 1640 can interact with audio subsystem 1620 and/or display subsystem 1630. For example, input through a microphone or other audio device can provide input or commands for one or more applications or functions of the computing device 1600. Additionally, audio output can be provided instead of, or in addition to display output. In another example, if display subsystem 1630 includes a touch screen, the display device also acts as an input device, which can be at least partially managed by I/O controller 1640. There can also be additional buttons or switches on the computing device 1600 to provide I/O functions managed by I/O controller 1640.

[00102] In some embodiments, I/O controller 1640 manages devices such as accelerometers, cameras, light sensors or other environmental sensors, or other hardware that can be included in the computing device 1600. The input can be part of direct user interaction, as well as providing environmental input to the system to influence its operations (such as filtering for noise, adjusting displays for brightness detection, applying a flash for a camera, or other features). [00103] In some embodiments, computing device 1600 includes power management 1650 that manages battery power usage, charging of the battery, and features related to power saving operation. Memory subsystem 1660 includes memory devices for storing information in computing device 1600. Memory can include nonvolatile (state does not change if power to the memory device is interrupted) and/or volatile (state is indeterminate if power to the memory device is interrupted) memory devices. Memory subsystem 1660 can store application data, user data, music, photos, documents, or other data, as well as system data (whether long-term or temporary) related to the execution of the applications and functions of the computing device 1600.

[00104] Elements of embodiments are also provided as a machine-readable medium (e.g., memory 1660) for storing the computer-executable instructions (e.g., instructions to implement any other processes discussed herein). The machine-readable medium (e.g., memory 1660) may include, but is not limited to, flash memory, optical disks, CD-ROMs, DVD ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, phase change memory (PCM), or other types of machine-readable media suitable for storing electronic or computer- executable instructions. For example, embodiments of the disclosure may be downloaded as a computer program (e.g., BIOS) which may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals via a communication link (e.g., a modem or network connection).

[00105] In some embodiments, computing device 1600 comprises connectivity 1670. Connectivity 1670 includes hardware devices (e.g., wireless and/or wired connectors and communication hardware) and software components (e.g., drivers, protocol stacks) to enable the computing device 1600 to communicate with external devices. The computing device 1600 could be separate devices, such as other computing devices, wireless access points or base stations, as well as peripherals such as headsets, printers, or other devices.

[00106] Connectivity 1670 can include multiple different types of connectivity. To generalize, the computing device 1600 is illustrated with cellular connectivity 1672 and wireless connectivity 1674. Cellular connectivity 1672 refers generally to cellular network connectivity provided by wireless carriers, such as provided via GSM (global system for mobile communications) or variations or derivatives, CDMA (code division multiple access) or variations or derivatives, TDM (time division multiplexing) or variations or derivatives, or other cellular service standards. Wireless connectivity (or wireless interface) 1674 refers to wireless connectivity that is not cellular, and can include personal area networks (such as Bluetooth, Near Field, etc.), local area networks (such as Wi-Fi), and/or wide area networks (such as WiMax), or other wireless communication.

[00107] In some embodiments, computing device 1600 comprises peripheral connections 1680. Peripheral connections 1680 include hardware interfaces and connectors, as well as software components (e.g., drivers, protocol stacks) to make peripheral connections. It will be understood that the computing device 1600 could both be a peripheral device ("to" 1682) to other computing devices, as well as have peripheral devices ("from" 1684) connected to it. The computing device 1600 commonly has a "docking" connector to connect to other computing devices for purposes such as managing (e.g., downloading and/or uploading, changing, synchronizing) content on computing device 1600. Additionally, a docking connector can allow computing device 1600 to connect to certain peripherals that allow the computing device 1600 to control content output, for example, to audiovisual or other systems.

[00108] In addition to a proprietary docking connector or other proprietary connection hardware, the computing device 1600 can make peripheral connections 1680 via common or standards-based connectors. Common types can include a Universal Serial Bus (USB) connector (which can include any of a number of different hardware interfaces), DisplayPort including MiniDisplayPort (MDP), High Definition Multimedia Interface (HDMI), Firewire, or other types.

[00109] Reference in the specification to "an embodiment," "one embodiment," "some embodiments," or "other embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments. The various appearances of "an embodiment," "one embodiment," or "some embodiments" are not necessarily all referring to the same embodiments. If the specification states a component, feature, structure, or characteristic "may," "might," or "could" be included, that particular component, feature, structure, or characteristic is not required to be included. If the specification or claim refers to "a" or "an" element, that does not mean there is only one of the elements. If the specification or claims refer to "an additional" element, that does not preclude there being more than one of the additional element.

[00110] Furthermore, the particular features, structures, functions, or characteristics may be combined in any suitable manner in one or more embodiments. For example, a first embodiment may be combined with a second embodiment anywhere the particular features, structures, functions, or characteristics associated with the two embodiments are not mutually exclusive.

[00111] While the disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations of such embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description. The embodiments of the disclosure are intended to embrace all such alternatives, modifications, and variations as to fall within the broad scope of the appended claims.

[00112] In addition, well known power/ground connections to integrated circuit (IC) chips and other components may or may not be shown within the presented figures, for simplicity of illustration and discussion, and so as not to obscure the disclosure. Further, arrangements may be shown in block diagram form in order to avoid obscuring the disclosure, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements are highly dependent upon the platform within which the present disclosure is to be implemented (i.e., such specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the disclosure, it should be apparent to one skilled in the art that the disclosure can be practiced without, or with variation of, these specific details. The description is thus to be regarded as illustrative instead of limiting.

[00113] The following examples pertain to further embodiments. Specifics in the examples may be used anywhere in one or more embodiments. All optional features of the apparatus described herein may also be implemented with respect to a method or process.

[00114] Example 1. An apparatus comprising: a magnetic junction including: a first structure comprising a magnet with a first perpendicular magnetic anisotropy (PMA), wherein the first structure has an anisotropy axis perpendicular to a plane of a device; a second structure comprising one of a dielectric or metal, the second structure being adjacent to the first structure; and a third structure comprising a magnet with a second PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures; and an interconnect adjacent to the magnetic junction; and a fourth structure comprising a magnet with the second PMA, wherein the fourth structure is adjacent to the interconnect, wherein the fourth structure has a magnetization which is opposite to a magnetization of the third structure, and wherein the first PMA is smaller than the second PMA. [00115] Example 2. The apparatus of example 1, wherein the interconnect comprises a material exhibiting spin orbit coupling.

[00116] Example 3. The apparatus according to any one of preceding examples, wherein the fourth structure comprises a first material and a second material different from the first material, and wherein the first and second materials are in a stack.

[00117] Example 4. The apparatus of example 3, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy.

[00118] Example 5. The apparatus of example 4, wherein the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.

[00119] Example 6. The apparatus of example 3, wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.

[00120] Example 7. The apparatus of example 3, wherein the first material has a thickness in a range of 0.6 nm to 2 nm, and wherein the second material has a thickness in a range of 0.1 nm to 3 nm.

[00121] Example 8. The apparatus according to any one of preceding examples, wherein the dielectric comprises: Mg and O.

[00122] Example 9. The apparatus of example 1, wherein the fourth structure comprises a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy, and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.

[00123] Example 10. The apparatus of example 1, wherein the fourth structure is adjacent to the interconnect such that the magnetic junction is adjacent to a first surface of the interconnect, wherein the fourth structure is adjacent to a second surface of the interconnect, and wherein the second surface is opposite to the first surface.

[00124] Example 11. The apparatus according to any one of preceding examples, wherein the interconnect is to generate spin Hall effect (SHE).

[00125] Example 12. The apparatus according to any one of preceding examples, wherein the interconnect includes one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b-W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth, elements of 3d, 4d, 5d and 4f, 5f periodic groups, graphene, Ti, S, W, Mo, Se, Sb, B, Re, La, C, P, O, As, Sc, Ga, Al, Y, In, Ce, Pr, Nd, Sr, or F.

[00126] Example 13. The apparatus of example 1, wherein the interconnect comprises spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material. [00127] Example 14. The apparatus of example 1, wherein the interconnect comprises a spin orbit material which includes materials that exhibit Rashba-Bychkov effect.

[00128] Example 15. The apparatus according to any one of preceding examples, wherein the magnetic junction is one of a spin valve or a magnetic tunneling junction (MTJ).

[00129] Example 16. The apparatus of example 1, wherein the magnet of the fourth structure is a paramagnet which includes one or more of: Pt, Pd, W, Ce, Al, Li, Mg, Na, Cr, O, Co, Dy, Er, Eu, Gd, Fe, Nd, K, Pr, Sm, Tb, Tm, or V.

[00130] Example 17. The apparatus of example 1, wherein the magnet of the fourth structure is a paramagnet which comprises dopants which include one or more of: Ce, Cr,

Mn, Nb, Mo, Tc, Re, Nd, Gd, Tb, Dy, Ho, Er, Tm, or Yb.

[00131] Example 18. A system comprising: a memory; a processor coupled to the memory, the processor having a spin wave switch, which comprises an apparatus according to any one of apparatus examples 1 to 17; and a wireless interface to allow the processor to communicate with another device.

[00132] Example 19. An apparatus comprising: a magnetic junction including: a first structure comprising a magnet with a first in-plane magnetic anisotropy, wherein the first structure has an anisotropy axis parallel to a plane of a device; a second structure comprising one of a dielectric or metal, the second structure being adjacent to the first structure; and a third structure comprising a magnet with a second in-plane magnetic anisotropy, wherein the third structure has an anisotropy axis parallel to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures; and an interconnect adjacent to the magnetic junction; and a fourth structure comprising a magnet with the second in-plane magnetic anisotropy, wherein the fourth structure is adjacent to the interconnect, wherein the fourth structure has a

magnetization which is opposite to a magnetization of the third structure, and wherein the first in-plane magnetic anisotropy is smaller than the second in-plane magnetic anisotropy.

[00133] Example 20. The apparatus of example 19 according to any one of claims 2 to 18.

[00134] Example 21. A system comprising: a memory; a processor coupled to the memory, the processor having a spin wave switch, which comprises an apparatus according to any one of apparatus examples 19 to 20; and a wireless interface to allow the processor to communicate with another device.

[00135] Example 22. A method comprising: forming a magnetic junction including: forming a first structure comprising a magnet with a first perpendicular magnetic anisotropy (PMA), wherein the first structure has an anisotropy axis perpendicular to a plane of a device; forming a second structure comprising one of a dielectric or metal, the second structure being adjacent to the first structure; and forming a third structure comprising a magnet with a second PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures; and forming an interconnect adjacent to the magnetic junction; and forming a fourth structure comprising a magnet with the second PMA, wherein the fourth structure is adjacent to the interconnect, wherein the fourth structure has a magnetization which is opposite to a magnetization of the third structure, and wherein the first PMA is smaller than the second PMA.

[00136] Example 23. The method of example 22, wherein the interconnect comprises a material exhibiting spin orbit coupling.

[00137] Example 24. The method according to any one of preceding method examples, wherein forming the fourth structure comprises forming a first material and a second material different from the first material, and wherein the first and second materials are in a stack.

[00138] Example 25. The method of example 24, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy.

[00139] Example 26. The method of example 25, wherein the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.

[00140] Example 27. The method of example 25, wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.

[00141] Example 28. The method of example 27, wherein the first material has a thickness in a range of 0.6 nm to 2 nm, and wherein the second material has a thickness in a range of 0.1 nm to 3 nm.

[00142] Example 29. The method according to any one of preceding method examples, wherein the dielectric comprises: Mg and O.

[00143] Example 30. The method of example 22, wherein forming the fourth structure comprises forming a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy, and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.

[00144] Example 31. The method of example 22, wherein forming the fourth structure adjacent to the interconnect such that the magnetic junction is adjacent to a first surface of the interconnect, wherein the fourth structure is adjacent to a second surface of the interconnect, and wherein the second surface is opposite to the first surface.

[00145] Example 32. The method according to any one of preceding method examples, wherein the interconnect is to generate spin Hall effect (SHE).

[00146] Example 33. The method according to any one of preceding method examples, wherein the interconnect includes one or more or: b-Tantalum (b-Ta), Ta, b- Tungsten (b-W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth, or elements of 3d, 4d, 5d and 4f, 5f periodic groups, graphene, Ti, S, W, Mo, Se, Sb, B, Re, La, C, P, O, As, Sc, Ga, Al, Y, In, Ce, Pr, Nd, Sr, or F.

[00147] Example 34. The method of example 22, wherein forming the interconnect comprises forming a spin orbit material which includes one of a 2D material or a 3D material, and wherein the 3D material is thinner than the 2D material.

[00148] Example 35. The method of example 22, wherein forming the interconnect comprises forming a spin orbit material which includes materials that exhibit Rashba- Bychkov effect.

[00149] Example 36. The method according to any one of preceding method examples, wherein the magnetic junction is one of a spin valve or a magnetic tunneling junction (MTJ).

[00150] Example 37. The method of example 22, wherein the magnet of the fourth structure is a paramagnet which includes one or more of: Pt, Pd, W, Ce, Al, Li, Mg, Na, Cr, Co, O, Dy, Er, Eu, Gd, Fe, Nd, K, Pr, Sm, Tb, Tm, or V.

[00151] Example 38. The method of example 22, wherein the magnet of the fourth structure is a paramagnet which comprises dopants which include one or more of: Ce, Cr,

Mn, Nb, Mo, Tc, Re, Nd, Gd, Tb, Dy, Ho, Er, Tm, or Yb.

[00152] Example 39. A method comprising: forming a magnetic junction including: forming a first structure comprising a magnet with a first in-plane magnetic anisotropy, wherein the first structure has an anisotropy axis parallel to a plane of a device; forming a second structure comprising one of a dielectric or metal, the second structure being adjacent to the first structure; and forming a third structure comprising a magnet with a second in plane magnetic anisotropy, wherein the third structure has an anisotropy axis parallel to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures; and forming an interconnect adjacent to the magnetic junction; and forming a fourth structure comprising a magnet with the second in-plane magnetic anisotropy, wherein the fourth structure is adjacent to the interconnect, wherein the fourth structure has a magnetization which is opposite to a magnetization of the third structure, and wherein the first in-plane magnetic anisotropy is smaller than the second in-plane magnetic anisotropy.

[00153] An abstract is provided that will allow the reader to ascertain the nature and gist of the technical disclosure. The abstract is submitted with the understanding that it will not be used to limit the scope or meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.