BACKGROUND

[0001] Extending density of a recording media (e.g., a hard disk drive (HDD)) is desirable due to the increase in data collection. Sensing the recorded data is also desirable to enable use of denser recording media. However, existing magnetic recording media and associated sensing element cannot be scaled in size due to reduced magnetic barriers.

Another limitation of existing magnetic recording media is the difficulty in magnetic writing via Ampere fields because higher magnetic anisotropy is combined with smaller size leads. Further, multi-sensor readout is not feasible in purely ferromagnetic media.

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] Figs. 1A-B illustrate a three-dimensional (3D) view and corresponding cross- section, respectively, of a magnetic memory hard-disk drive (HDD) having multiferroic recording media, according to some embodiments of the disclosure.

[0004] Fig. 2 illustrates a 3D view of a multiferroic recording cell, according to some embodiments of the disclosure.

[0005] Fig. 3 illustrates a 3D view of a multiferroic recording cell, according to some embodiments of the disclosure.

[0006] Fig. 4 illustrates a 3D view of an apparatus with a multiferroic recording cell and an electrostatic writing electrode, according to some embodiments of the disclosure.

[0007] Fig. 5 illustrates a 3D view of an apparatus with a multiferroic recording cell and an electrostatic and a magnetic writing electrode, according to some embodiments of the disclosure.

[0008] Fig. 6 illustrates a 3D view of an apparatus with a multiferroic recording cell, two electrostatic writing electrodes for front-side and back-side simultaneous writing, and a magnet writing electrode, according to some embodiments of the disclosure.

[0009] Fig. 7 illustrates a 3D view of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes for front-side and back-side simultaneous writing, according to some embodiments of the disclosure. [0010] Fig. 8 illustrates a 3D view of an apparatus with a multiferroic recording cell and an electrostatic writing electrode for the back-side and a magnetic writing electrode for the front-side, according to some embodiments of the disclosure.

[0011] Fig. 9 illustrates a 3D view of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes with piezoresponse force microscopy (PFM) for front-side and back-side simultaneous writing, according to some embodiments of the disclosure.

[0012] Fig. 10 illustrates a 3D view of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes with PFM and with ferroelectric tips for front-side and back-side simultaneous writing, according to some embodiments of the disclosure.

[0013] Fig. 11 illustrates a 3D view of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes with PFM for front-side and back-side simultaneous writing, and with ferroelectric readout sensor, according to some embodiments of the disclosure.

[0014] Fig. 12 illustrates a 3D view of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes with PFM and with ferroelectric tips for front-side and back-side simultaneous writing, and with ferroelectric readout sensor, according to some embodiments of the disclosure.

[0015] Fig. 13 illustrates a smart device or a computer system or a SoC (System-on-

Chip) with a magnetic memory having multiferroic recording media and associated writing and reading sensors, according to some embodiments.

DETAILED DESCRIPTION

[0016] Various embodiments describe a magnetic recording media with multiferroic multi-layered media. In some embodiments, the magnetization stability or the magnetic recording media is enhanced by the ferroelectric state of the multiferroic media. In some embodiments, the magnetic recording media comprises a ferromagnet (FM) layer coupled to a multiferroic medium such as BFO (e.g., BiFeCb). In some embodiments, the magnetic recording media can be written to using single or dual writing electrodes. For example, the magnetic recording media can be accessed from the front-side and/or back-side of the magnetic recording media and written to. In some embodiments, dielectric constant media (with high permittivity) is directly or indirectly coupled to the magnetic recording media to improve electric field localization. In some embodiments, a multi-sensor is provided which is used for reading the data from the magnetic recording media. As such, read-stability is improved.

[0017] There are many technical effects of the various embodiments. For example, denser recording media can be achieved due to multiferroic stabilization. In some embodiments, faster writing (than traditional writing processes) is achieved by simultaneous writing via multiple writing electrodes. Other technical effects will be evident from the various embodiments and figures.

[0018] In the following description, numerous details are discussed to provide a more thorough explanation of the 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.

[0019] 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.

[0020] 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. 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. 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. 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."

[0021] The terms "substantially," "close," "approximately," "near," and "about," generally refer to being within +/- 10% of a target value (unless specifically specified). 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.

[0022] 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). 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.

[0023] Figs. 1A-B illustrate a three-dimensional (3D) view 100 and corresponding cross-section 120, respectively, of a magnetic memory hard-disk drive (HDD) having multiferroic recording media, according to some embodiments of the disclosure. In some embodiments, HDD comprises a substrate 101 (e.g., glass substrate, sapphire substrate, etc.), a heat spreading layer 102, transition metal layer 103, multiferroic recording media 104, and cladding layer 105.

[0024] In some embodiments, after substrate 101 is formed, heat spreading layer 102 is deposited above substrate 101. In some embodiments, layer 102 has high permittivity. Here, permittivity indicates how much electric field or flux is generated per unit charge in the recording media. Permittivity relates to a materials' ability to resist an electric field.

Permittivity is related to electric susceptibility (e.g., a measure of how easily a dielectric polarizes in response to an electric field). In some embodiments, layer 102 is formed of Ru and similar materials.

[0025] In some embodiments, when layer 101 comprises sapphire substrate and layer

102 has a material with high permittivity, magnetic recording medium 104 can be written to using back-side of HDD 100. For example, a write electrode (e.g., an electrode providing electrostatic field) can be applied to layer 101 to write to one or more cells of multiferroic recording media 104. In some embodiments, transition metal layer 103 is formed above heat spreading layer 102. In some embodiments, transition metal layer 103 is formed of strain producing substrates such as BTO (e.g., B112T1O20 or Bi4T Oi ₂ .), DySCCb, GaAs, and group III-V substrates. In some embodiments, transition metal layer 103 is formed of one of: Mo, Pd, Cr, Pt, or CoCrPt. In some embodiments, transition metal layer 103 is formed of Mo (110) face centered cubic (FCC) lattice.

[0026] In some embodiments, magnetic recording layer (or medium) 104 is grown above transition metal layer 103. The magnetic recording layer 104 is used for reading and writing data by storing data in magnetic elements or cells arranged in an array (e.g., rows and columns of magnetic elements or components). In some embodiments, magnetic recording layer 104 comprises multiferroic materials. For example, magnetic recording layer 104 comprises a ferromagnet layer and one or more layers of multiferroic material (e.g., Bismuth ferrite (BFO)). Multiferroic materials are materials that exhibit one or more ferroic order parameters simultaneously (e.g., ferroic order parameters such as ferromagnetism, ferroelectricity, or ferro-elasticit ). Various embodiments here focus on the ferromagnetism ferroic order parameter. BFO such as BiFeC is a multiferroic material that has good ferroelectric and antiferromagnetic properties. Other examples of multiferroic material include BiMn03, PbV03, magnetic perovskite materials (e.g., PZTFT such as

PbZro.53Tio.4703)o.6), rare-earth manganite materials (e.g., TbMn03 and HoMmOs), non- perovskite multiferroic oxides (e.g., LuFe204 and L1CU2O3), non-perovskite multiferroic non- oxides (e.g., BaNiF4), spinel chalcogenides (e.g., ZnCr2Se4), h-YMn03, K3Se04, Cs2Cd , M3V2O8, MnW0 ₄ , and CuO, etc.

[0027] The magnetic recording layer 104 may not be a continuous layer. Instead, in some examples, as shown in Fig. 1A, the magnetic recording layer 104 comprises magnetic recording cells (or dots) organized in rows and columns. Each dot or cell is akin to a memory bit-cell which stores certain data.

[0028] In some embodiments, cladding layer 105 or lubricant 105 is deposited over magnetic recording layer 104 so that a sensor or tip to read and write to magnetic elements can slide over magnetic recording layer 104 smoothly. An example of cladding layer 105 or lubricant 105 is a layer of perfluoropoly ether (PFPE) which is a chain polymer of fluorine, carbon, and oxygen atoms. In some embodiments, cladding layer 105 or lubricant 105 is a layer that includes one of: Z-Type Perfluoro Poly Ether Lubricant Polymers, Z-Dol 4000 or Z-Tetroal, ZDol 7800, or Cyclotriphosphazenes.

[0029] Fig. 2 illustrates 3D view 200 of a multiferroic recording cell, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 2 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. In this example one multiferroic recording cell 104 is shown coupled between layers 105 and 103. In some embodiments, multiferroic recording cell 104 comprises ferromagnet (FM) 201 and multiferroic material 202. In some embodiments, FM 201 is a free magnet which is also coupled to layer 105. Here, the term "free magnet" generally refers to a magnet such as a ferromagnet whose magnetization is not predetermined or pinned, and whose magnetization can be altered by an external stimulus. In some embodiments, multiferroic material 202 is coupled to layer 103. Here, multiferroic material 202 provides exchange coupling with FM 201. In some embodiments, magnetization of FM 201 is switched by applying an electric field Έ' to multiferroic recording cell 104. The electric field Έ' controls the magnetic field. Since the electric field Έ' is stable, the magnetic field becomes stable too. For example, when electric field Έ' does not change in the multiferroic material 202, the magnetic field in FM 201 does not change. As such, the overall stability of the multiferroic recording cell increases compared to traditional magnetic recording cells.

[0030] In some embodiments, FM 201 comprises a material selected from a group consisting of: Fe, Ni, Co and their alloys, magnetic insulators, and Heusler alloys of the form X?.YZ. In some embodiments, the magnetic insulators comprise a material selected from a group consisting of: magnetite Fe ₃ 0 ₄ and Y3AI5O12. In some embodiments, the Heusler alloys comprises one or more of the elements: Mn, Al, Co, Fe, Ge, Ga, Cu, In, Sn, Ni, Sb, Pd, In, Val, or V. In some embodiments, the Heusler alloys is one of: MmGa, Co2FeAl, Co ₂ FeGeGa, 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, Fe ₂ Val, Mn ₂ VGa, and Co ₂ FeGe. In some embodiments, the threshold energy for FM 201 is in the range of 20-60 kT, where 'k' is Boltzmann constant and 'Τ' is temperature. In the following example, the threshold energy for FM 201 is considered to be 40 kT.

[0031] In some embodiments, FM 201 is formed with a sufficiently low anisotropy

(Hk) to facilitate switching by exchange bias and sufficiently high magnetic saturation (M _s ) to ensure sufficient threshold energy and thus stability. Magnetic saturation M _s is generally the state reached when an increase in applied external magnetic field H cannot increase the magnetization of the material (i.e., total magnetic flux density B substantially levels off). Anisotropy Hk generally refers to the material property which is directionally dependent. Materials with anisotropy are materials with material properties that are highly directionally dependent.

[0032] In some embodiments, multiferroic material 202 comprises BFO such as

BiFeC which is a multiferroic material that has good ferroelectric and antiferromagnetic properties: high enough values of saturated ferroelectric polarization P _s , antiferromagnetic order parameter L, and uncompensated magnetization M _c . Other examples of multiferroic material 202 include BiMnCb, PbVCb, magnetic perovskite materials (e.g., PZTFT such as PbZro.53Tio.4703)o.6), rare-earth manganite materials (e.g., TbMn03 and HoMmOs), non- perovskite multiferroic oxides (e.g., LuFe204 and L1CU2O3), non-perovskite multiferroic non- oxides (e.g., BaNiF4), spinel chalcogenides (e.g., ZnCr2Se4), h-YMn03, K3Se04, Cs2Cdl4, N13V2O8, MnW04, and CuO, etc. In some embodiments, multiferroic material 202 includes one or more of the elements: Bi, Mn, O, Pb, V, Ti, Zr, Tb, Ho, Lu, Cu, Ba, Ni, F, Zn, Cr, Se, Y, K, Cs, and W.

[0033] Fig. 3 illustrates 3D view 300 of a multiferroic recording cell, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 3 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. Multiferroic recording cell 104 of Fig. 3 is similar to multiferroic recording cell 104 of Fig. 2 except that it includes a layer of another multiferroic material 301. In some embodiments, multiferroic material 301 is formed on top of FM 201 such that multiferroic material 301 couples layer 105. In some embodiments, multiferroic material 301 is formed of the same material as multiferroic material 202. For example, both multiferroic materials 202 and 301 are BFO materials. In this embodiment, exchange bias is exerted by multiferroic 202 on the bottom surface of FM 201 and by multiferroic 301 on the top surface of FM 201. This exchange bias effectively doubles the torque which switches the magnetization.

[0034] Fig. 4 illustrates three dimensional (3D) view 400 of an apparatus with a multiferroic recording cell and an electrostatic writing electrode, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 4 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. Fig. 4 is similar to Fig. 2 except that an electrode is added to write to the front-side of multiferroic recording cell 104. Here, the term "front-side" generally refers to the part of multiferroic recording cell 104 that is coupled to layer 105, while the term "back-side" generally refers to the part of multiferroic recording cell 104 that is coupled to layer 103.

[0035] In some embodiments, the electrodes include a tip 401 attached to a cantilever

402. In some embodiments, the shape of tip 401 is configured to provide focused electrostatic field to multiferroic recording cell 104. In some embodiments, electrostatic field is generated by a voltage applied to cantilever 402. In some embodiments, cantilever 402 may be attached to a mechanical arm that moves the cantilever to the memory cell that needs to be written to. The electrostatic field from tip 401 controls the magnetic field in FM 201. The shape of tip 401 can be configured to focus the electric field to multiferroic recording cell 104 such that other multiferroic recording cells in the recording media are not affected. Depending on the direction of the electric field provided by tip 401, a certain magnetization is stored in FM 201. For example, when electric field is directed towards layer 103, FM 201 may have a magnetization pointing in the North direction. Likewise, when an electric field is directed towards layer 105, FM 201 may have a magnetization pointing in the South direction. In this example, FM 201 is a perpendicular free magnet. However, the same concept can apply to in-plane FM 201.

[0036] Fig. 5 illustrates 3D view 500 of an apparatus with a multiferroic recording cell and an electrostatic and a magnetic writing electrode, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 5 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. Fig. 5 is similar to Fig. 4 except that an additional electrode 501 is provided. In some embodiments, the additional electrode 501 is a magnetic tip which provides further magnetic field to FM 201 so that it strongly writes data to memory cell 104. In some embodiments, electrode 501 is a free magnet with

magnetization set according to the desired magnetization of FM 201. In some embodiments, when FM 201 is a perpendicular magnet, magnetic electrode 501 is also magnetized along the same line which is perpendicular to the plane of the substrate. In some embodiments, FM 201 is an in-plane magnet, magnetic electrode 501 is also magnetized in the plane of the substrate. In some embodiments, the magnetization of electrode 501 is set according to the direction of electric field generated by tip 401 so that the magnetic fields produced by the electric field from tip 401 and electrode 501 have the same direction. As such, it becomes easier to cross the energy barrier of FM 201 to change its magnetization to the desired magnetization. The direction of magnetization dictates the value stored in multiferroic recording cell 500.

[0037] Fig. 6 illustrates 3D view 600 of an apparatus with a multiferroic recording cell, two electrostatic writing electrodes for front-side and back-side simultaneous writing, and a magnet writing electrode, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 6 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. Fig. 6 is similar to Fig. 5 except that an additional electrode is provided for writing via the back-side of the HDD. In some embodiments, the additional electrode includes cantilever 602 and tip 601. Construction wise, cantilever 602 and tip 601 may be similar to cantilever 402 and tip 401. In some embodiments, tip 401 may be providing electrostatic field to one multiferroic recording cell while tip 601 is providing electrostatic field to another multiferroic recording cell. As such, multiple multiferroic recording cells of the same HDD may be written to by two different electrodes,

simultaneously. In some embodiments, the same cell may be written to using three different sources (e.g., tip 401 , magnetic electrode 501 , and tip 601) so that the magnetization of FM 201 is set with high degree of confidence. As such, writing speed can increase because FM 201 can be written to faster when compared to the case of writing using one electrode, for example.

[0038] Fig. 7 illustrates 3D view 700 of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes for front-side and back-side simultaneous writing, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 7 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. Fig. 7 is similar to Fig. 6 except magnetic electrode 501 is removed. Like Fig. 6, here FM 201 can be written to from front-side or back-side of HDD. For example, tip

401 is used to write to FM 201 via the front-side while tip 601 is used to write to FM 201 via the back-side of HDD.

[0039] Fig. 8 illustrates 3D view 800 of an apparatus with a multiferroic recording cell and an electrostatic writing electrode for the back-side and a magnetic writing electrode for the front-side, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 8 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. Fig. 8 is similar to Fig. 6 except that electrostatic tip 401 and its cantilever

402 are removed. Like Fig. 6, here FM 201 can be written to from the front-side and/or the back-side of HDD. For example, magnetic electrode 501 is used to write to FM 201 via the front-side while tip 601 is used to write to FM 201 via the back-side of HDD. Compared to Fig. 6, an additional layer 801 is sandwiched between multiferroic material 202 and layer 103. In some embodiments, layer 801 comprises one of Sapphire, SiC, or diamond. In some embodiments, the shape of tip 601 is enhanced to provide electrostatic field with high numerical aperture (NA).

[0040] Fig. 9 illustrates 3D view 900 of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes with PFM for front-side and back-side simultaneous writing, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 9 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. In some embodiments, the front-side writing apparatus (e.g., tip 401 and cantilever 402) is replaced with PFM capable tip 901 and cantilever 902. PFM allows manipulation of ferroelectric materials. In some embodiments, an alternating current (AC) is applied to tip 901 via cantilever 902 to excite deformation of multiferroic recording cell 104. In some embodiments, the back-side writing apparatus (e.g., tip 601 and cantilever 602) is replaced with PFM capable tip 903 and cantilever 904. Material and structure wise, PFM capable tip 903 and cantilever 904 is same as PFM capable tip 901 and cantilever 902, respectively.

[0041] In some embodiments, tip 901 may be providing electrostatic field to one multiferroic recording cell while tip 903 is providing electrostatic field to another multiferroic recording cell. As such, multiple multiferroic recording cell of the same HDD may be written to by two different electrodes, simultaneously. In some embodiments, the same cell may be written to using two different sources (e.g., tip 901 and tip 903) so that the magnetization of FM 201 is set with high degree of confidence. As such, writing speed can increase because FM 201 can be written to faster compared to the case when writing using one electrode, for example.

[0042] Fig. 10 illustrates 3D view 1000 of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes with PFM and with ferroelectric tips for front- side and back-side simultaneous writing, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 10 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. Fig. 10 is similar to Fig. 9 except that the tips of the writing electrodes are replaced with ferroelectric tips like 1001 (e.g., like 401) and 1003 (e.g., 601).

[0043] Fig. 11 illustrates 3D view 1100 of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes with PFM for front-side and back-side simultaneous writing, and with ferroelectric readout sensor, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 11 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. Fig. 11 is similar to Fig. 9 except that a reading sensor is added which comprises free magnet 1101, fixed magnet 1102, and nonmagnetic conductor 1103 (e.g., Cu, Al, Au, Ag, etc.) coupling the two magnets. In some embodiments, the free magnet 1101 is positioned near the multiferroic recording cell which is to be read. The reading is performed using GMR (Giant magnetoresistance).

[0044] In some embodiments, first and second magnets 1101 and 1102 are ferromagnets that are made from CFGG (i.e., Cobalt (Co), Iron (Fe), Germanium (Ge), or Gallium (Ga) or a combination of them). In some embodiments, first and second magnets 1101 and 1102 are formed from Heusler alloy(s). Heusler alloy is ferromagnetic metal alloy based on a Heusler phase. Heusler phase is intermetallic with certain composition and face- centered cubic (FCC) crystal structure. The ferromagnetic property of the Heusler alloy is a result of a double-exchange mechanism between neighboring magnetic ions.

[0045] In some embodiments, the thickness t _c of first and second magnets 1101 and

1102, respectively, may determine its magnetization direction. For example, when the thickness of a ferromagnetic layer is above a certain threshold (depending on the material of the magnet, e.g., approximately 1.5 nm for CoFe), then the ferromagnetic layer exhibits magnetization direction which is in-plane. Likewise, when the thickness of the ferromagnetic layer is below a certain threshold (depending on the material of the magnet), then the ferromagnetic layer exhibits magnetization direction which is perpendicular to the plane of the magnetic layer. Other factors may also determine the direction of magnetization. In some embodiments, first and second magnets 1101 and 1102 have out-of-plane magnetization (e.g., pointing in the +/- z-direction). In some embodiments, first and second magnets 1101 and 1102 have in-plane magnetization (e.g., pointing in the +/- x or +/- y direction).

[0046] For example, factors such as surface anisotropy (depending on the adjacent layers or a multi-layer composition of the ferromagnetic layer) 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.

[0047] In some embodiments, when FM 201 has in-plane magnetization (e.g., point in

+x or -x direction depending on how it is programmed by tips 901/903), free and fixed magnets 1101 and 1102, respectively, also have in-plane magnetizations. In some embodiments, when FM 201 has perpendicular magnetization (e.g., point in +z or -z direction depending on how it is programmed by tips 901/903), free and fixed magnets 1101 and 1102, respectively, also have perpendicular magnetizations.

[0048] Fig. 12 illustrates 3D view 1200 of an apparatus with a multiferroic recording cell and two electrostatic writing electrodes with PFM and with ferroelectric tips for front- side and back-side simultaneous writing, and with ferroelectric readout sensor, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 12 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. Fig. 12 is similar to Fig. 10 except with reading sensor of Fig. 11.

[0049] Fig. 13 illustrates a smart device or a computer system or a SoC (System-on-

Chip) with a magnetic memory using multiferroic recording media (which are written to and read from using the sensors described here), according to some embodiments. It is pointed out that those elements of Fig. 13 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.

[0050] 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.

[0051] Fig. 13 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.

[0052] In some embodiments, computing device 1600 includes first processor 1610 and 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. [0053] 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.

[0054] 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.

[0055] 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.

[0056] 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. [0057] 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.

[0058] 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).

[0059] 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. In some embodiments, Memory subsystem 1660 includes the scheme of analog in-memory partem matching with the use of resistive memory elements. In some embodiments, memory subsystem includes a magnetic memory HDD using multiferroic recording media (which are read using the sensors described here), according to some embodiments.

[0060] 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).

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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. [0069] 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.

[0070] Example 1 is an apparatus which comprises: a first layer for heat spreading; a second layer comprising a transition metal, wherein the second layer is adjacent to the first layer; and a third layer comprising a magnetic recording medium, wherein the third layer is adjacent to the second layer, wherein the third layer comprises: a fourth layer comprising ferromagnetic material; and a fifth layer comprising multiferroic material, wherein the fourth layer is adjacent to the fifth layer.

[0071] Example 2 includes all features of example 1, wherein the magnetic recording medium comprises a sixth layer comprising multiferroic material, wherein the sixth layer is adjacent to the fourth layer such that the fourth layer is sandwiched between the fifth and sixth layers.

[0072] Example 3 includes all features of example 2, wherein the magnetic recording medium comprises a seventh layer comprising an insulating material sandwiched between the fifth layer and the second layer.

[0073] Example 4 includes all features of example 3, wherein the insulating material comprises a material which includes one of: Al, O, Si, C, sapphire, SiC, or diamond.

[0074] Example 5 includes all features of example 2, wherein the multiferroic material of the fifth and sixth layers comprises a material which includes one of: Bi, Fe, or O.

[0075] Example 6 includes features of any one of examples 1 to 4, wherein the multiferroic material of the fifth layer comprises a material which includes one of: Bi, Fe, or O.

[0076] Example 7 includes features of any one of examples 1 to 5, wherein the second layer comprises a material selected from which includes one of: Mo, Pd, Cr, Pt, or CoCrPt.

[0077] Example 8 includes features of any of examples 1 to 5, wherein the apparatus of example 8 comprises a substrate adjacent to the heat spreading layer.

[0078] Example 9 includes features of example 8, wherein the substrate is a glass substrate.

[0079] Example 10 includes features according to any one of examples 1 to 5, wherein the third layer is written to via a first mechanical tip that is to provide a first electrostatic field to the third layer, wherein the first mechanical tip is closer to the fourth layer than the fifth layer. [0080] Example 11 includes all features of example 10, wherein the third layer is written to via a magnet that is to provide a magnetic field which is controlled by the first electrostatic field from the first mechanical tip.

[0081] Example 12 includes all features of example 10, wherein the third layer is written to via a second mechanical tip that is to provide a second electrostatic field to the third layer, wherein the second mechanical tip is closer to the fifth layer than the fourth layer.

[0082] Example 13 includes all features of example 12, wherein the first and second mechanical tips apply piezoresponse force microscopy (PFM) to the fourth and fifth layers, respectively.

[0083] Example 14 includes all features of example 13, wherein the first and second mechanical tips are ferroelectric tips.

[0084] Example 15 includes all features of example 13, wherein the third layer is read from via free magnet coupled to a fixed magnet via a non-magnetic metal.

[0085] Example 16 according to any one of examples 1 to 5, wherein the apparatus of example 16 comprises a cladding layer adjacent to the magnetic recording medium, wherein the cladding layer comprises a material which includes one of: F, C, O, perfluoropolyether (PFPE), Z-Type Perfluoro Poly Ether Lubricant Polymer, Z-Dol 4000, Z-Tetroal, ZDol 7800, or Cyclotriphosphazenes,

[0086] Example 17 according to any one of examples 1 to 5, wherein the magnetic recording medium includes a plurality of magnetic components organized in an array configuration.

[0087] Example 18 according to any one of examples 1 to 5, wherein the fourth layer comprises a material which includes one of: Fe, Ni, Co and their alloys, magnetic insulators, orHeusler alloys of the form XiYZ.

[0088] Example 19 includes all features of example 13, wherein the magnetic insulators comprise a material which includes one of: Fe, O, Y, Al, magnetite Fe ₃ 0 ₄ , or

[0089] Example 20 includes all features of example 13, wherein the Heusler alloys includes one of: Mn, Ga, Co, Mn, Ge, Co, Fe, Al, Cu, In, Sn, Ni, Sn, Sb, Si, Pd, V, M Ga, Co ₂ FeAl, Co ₂ FeGeGa, 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, Fe ₂ Val, Mn ₂ VGa, or Co ₂ FeGe.

[0090] Example 21 is a system which comprises: a processor; a memory coupled to the processor, the memory including an apparatus according to any one of apparatus examples 1 to 20; and a wireless interface for allowing the processor to communicate with another device.

[0091] Example 22 is a method which comprises: forming a first layer for heat spreading; forming a second layer comprising a transition metal, wherein the second layer is adjacent to the first layer; and forming a third layer comprising a magnetic recording medium, wherein the third layer is adjacent to the second layer, wherein the third layer comprises: a fourth layer comprising ferromagnetic material; and a fifth layer comprising multiferroic material, wherein the fourth layer is adjacent to the fifth layer such that the fifth layer is adjacent to the second layer.

[0092] Example 23 includes all features of example 22, wherein the magnetic recording medium comprises a sixth layer comprising multiferroic material, wherein the sixth layer is adjacent to the fourth layer such that the fourth layer is sandwiched between the fifth and sixth layers.

[0093] Example 24 includes all features of example 23, wherein the magnetic recording medium comprises a seventh layer comprising an insulating material sandwiched between the fifth layer and the second layer, wherein the insulating material comprises a material which comprises: Al, O, Si, C, sapphire, SiC, or diamond.

[0094] Example 25 includes all features of example 23, wherein the multiferroic material of the fifth and sixth layers comprises a material which includes one of: Bi, Fe, or O.

[0095] Example 26 according to any one of examples 21 to 25, wherein the multiferroic material of the fifth layer comprises a material which includes one of: Bi, Fe, or O.

[0096] Example 27 according to any one of examples 21 to 25, wherein the second layer comprises a material selected from a group which includes one of: Mo, Pd, Cr, Pt, or CoCrPt.

[0097] Example 28 according to any one of examples 21 to 25, wherein the method of example 28 comprises forming a substrate adjacent to the heat spreading layer.

[0098] Example 29 which includes features of example 28, wherein the substrate is a glass substrate.

[0099] Example 30 according to any one of example 21 to 25, wherein the method of example 30 comprises writing to the third layer via a first mechanical tip that is to provide a first electrostatic field to the third layer, wherein the first mechanical tip is closer to the fourth layer than the fifth layer. [00100] Example 31 includes all features of example 21, wherein the method of example 31 comprises writing to the third layer via a magnet that is to provide a magnetic field which is controlled by the first electrostatic field from the first mechanical tip.

[00101] Example 32 includes all features of example 30, wherein the method of example 32 comprises writing to the third layer via a second mechanical tip that is to provide a second electrostatic field to the third layer, wherein the second mechanical tip is closer to the fifth layer than the fourth layer.

[00102] Example 33 includes all features of example 32, wherein the method of example 33 comprises applying via the first and second mechanical tips piezoresponse force microscopy (PFM) to the fourth and fifth layers, respectively.

[00103] Example 34 includes all features of example 33, wherein the first and second mechanical tips are ferroelectric tips.

[00104] Example 35 includes all features of example 33, wherein the third layer is read from via free magnet coupled to a fixed magnet via a non-magnetic metal.

[00105] Example 36 according to any one of examples 21 to 25, wherein the method of example 36 comprises forming a cladding layer adjacent to the magnetic recording medium, wherein the cladding layer comprises a material which includes one of: F, C, O,

perfluoropoly ether (PFPE), Z-Type Perfluoro Poly Ether Lubricant Polymer, Z-Dol 4000, Z- Tetroal, ZDol 7800, or Cyclotriphosphazenes,

[00106] Example 37 according to any one of examples 21 to 25, wherein the magnetic recording medium includes a plurality of magnetic components organized in an array configuration.

[00107] Example 38 according to any one of examples 21 to 25, wherein the fourth layer comprises a material which includes one of: Fe, Ni, Co and their alloys, magnetic insulators, orHeusler alloys of the form XzYZ.

[00108] Example 40 includes all features of example 28, wherein the magnetic insulators comprise a material which includes one of: Fe, O, Y, Al, magnetite Fe ₃ 0 ₄ , or

[00109] Example 41 includes all features of example 38, wherein the Heusler alloys includes one of: Mn, Ga, Co, Mn, Ge, Co, Fe, Al, Cu, In, Sn, Ni, Sn, Sb, Si, Pd, V, M Ga, Co ₂ FeAl, Co ₂ FeGeGa, 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, Fe ₂ Val, Mn ₂ VGa, or Co ₂ FeGe. [00110] 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.