Background to the invention Magnetic recording disks and disk drives are conventionally employed for storing large amounts of data in a magnetic form. In the disk drive 10 shown in figure 1, data is written onto and read from a rapidly rotating recording disk 12 by means of a magnetic head transducer assembly 14 that flies close to the surface of the disk. The magnetic tape drive is a widely used alternative means of storing large amounts of data, especially for back-up data storage. A conventional tape drive 20 of the type represented in figure 2 is designed to transfer data to and from a length of magnetically encoded tape, which is carried on and transferred between a supply reel and a take-up reel contained within a tape cartridge 22. Data is written onto and read from the length of magnetic tape by means of a head assembly 24. Of the several tape drive designs used, the most widely used arrangements are the stationary head tape drive, the rotary head tape drive and the arcuate scan tape drive. In both the tape drive and the disk drive the head assembly may comprise a magnetic thin film head (TFH) 30, a representation of the salient features of which is shown in figure 3. The TFH comprises a write device and a read device. The write device comprises a top pole 42 and a bottom pole 34 with a non-magnetic write gap 38 in between.

The read device comprises a top shield 34 and a bottom shield 32 with a non-magnetic read gap 36 in between. A read element 40 is positioned within the read gap 36. Intervening layers have been omitted in figure 3 to emphasise the salient features of the TFH.

The increasing requirements for high areal recording density, small disk and tape drives and fast data transfer rates imposes increasingly demanding requirements on the performance of the head assembly. In recent years, in an attempt to produce drive systems that are capable of writing and reading high density data, the structure of the head assembly has been modified by merging the write and read components. In figure 3, the merged write bottom pole-read top shield is represented by component 34. However, the merging of the write bottom pole with the read top shield has resulted in a deterioration in the read signal caused by noise. After a write operation with such a merged head assembly, unstable remnant domain states are produced which relax in an unrepeatable and random manner.

The relaxation of the domain states is detected by the read device thereby introducing a significant noise component into the read signal. Furthermore, at high frequencies, in particular those above 200MHz, eddy current losses in thin-film heads become significant and reduce the performance of the write component.

More recently, considerable effort has been expended to overcome the reduction in performance caused by the merging of the write and read components. There has been a drive to develop techniques of subdividing the write bottom pole and read top shield into a series of magnetically isolated laminates by the use of conventional lamination schemes as described by Slonczewsi in Paper AA-01, Intermag'90, Brighton, UK. In such a conventional method of making a head assembly, alternating layers of magnetic and non- magnetic material are laminated and then patterned to form the desired structure. However, in such a conventional laminated structure edge curling domain walls are formed between the write top pole and the merged write bottom pole-read top shield. As shown in figure 4 the curling domain walls, which are represented by the arrows, extend beyond the outer edges of the write top pole 42 and merged write bottom pole-read top shield 34. The presence of the curling domain walls increases susceptibility to external magnetic fields.

US 5,673,163 describes a pinched-gap magnetic recording thin film head which is used for the recording of magnetic transitions on moving magnetic media. To prevent a reduction in read efficiency the write thin film head is positioned separately from a read head on an air-bearing slider.

"Edge closed laminated structures for thin films heads", D. A. Herman et al., J. Appl. Phys. 69 (8), p5424 (1991) describes magnetic film laminations containing non- magnetic spacers.

Thus, there is a need for a merged head assembly which is capable of achieving required data densities and transfer rates without compromising on data integrity.

Summary of the invention An object of the present invention is to provide a merged or combined read/write head assembly capable of recording and reading data at high areal recording densities.

Another object of the present invention is a merged or combined read/write head assembly capable of operating at high data transfer rates.

A further object of the present invention is a merged or combined read/write head assembly for a tape drive with improved pole wear and head assembly corrosion characteristics.

A further object of the present invention is a simplified process of manufacturing a merged or combined read/write head assembly.

Accordingly the present invention relates to a read/write head for a disk drive, comprising: a write top pole; a combined write pole and read shield; a write gap separating the write top pole and the combined write bottom pole and read top shield; and an edge shorting component disposed between and adjacent the write top pole and the combined write bottom pole and read top shield.

The present invention also provides a method of forming the read/write head, wherein the write top pole and/or the combined write bottom pole and read top shield are patterned in a series of steps, thereby obtaining thick magnetic layers by means of a series of thin photo-resist layers.

The edge shorting component of the present invention may comprise two elements, which are disposed at opposite ends of the read/write head easy axis towards the outer peripheral edges of the write top pole and the combined write bottom pole and read top shield.

Alternatively, the edge shorting component of the present invention may extend substantially around the periphery of the write top pole and the combined write bottom pole and read top shield.

Brief description of the drawings Embodiments of the present invention will now be described by way of further example only and with reference to the accompanying drawings, in which: Figure 1 is a representation of a disk drive system of the present invention; Figure 2 is a representation of a tape drive system of the present invention; Figure 3 shows salient features of a conventional merged thin-film head; Figure 4 shows edge curling domain fields in a conventional merged thin-film head; Figure 5 shows a first embodiment of the present invention; Figure 6 shows a plan view of the first embodiment of the invention; Figure 7 is a representation of a view of the first embodiment as presented to an air bearing surface; Figure 8 shows a plan view of a second embodiment of the present invention; Figure 9 is a representation of a view of the second embodiment as presented to an air bearing surface; and Figure 10 shows a head assembly contour enhancement according to the present invention.

Description of the invention A first embodiment of the present invention is shown in figure 5. The embodiment comprises a write top pole 42 and a merged write bottom pole-read top shield 34 separated by a write gap 38 of non-magnetic material. Preferably, the write bottom pole is combined with the read top shield, rather than the write bottom pole component being merged or joined with the read top shield component. Thus, the manufacture or structure of the head assembly is considerably simplified. The embodiment also comprises two edge shorting components 52 positioned adjacent and between the write top pole 42 and the merged or combined write bottom pole-read top shield 34 at either end of the"easy axis"54. Each edge shorting component may be aligned with the edge of the pole 42 or the shield 34, or may protrude from or may be recessed from the edge of the pole 42 or the shield 34.

Furthermore, the edges of the write top pole 42 and the merged or combined write bottom pole-read top shield 34 at either end of the"easy axis"may not be aligned with each other.

However, in a preferred embodiment the edges at either end of the"easy axis"of the write top pole 42, the merged or combined write bottom pole-read top shield 34 and the edge shorting component 52 are substantially aligned with each other. The write top pole 42, the merged or combined write bottom pole-read top shield 34 and the edge shorting components 52 are of a magnetic material. As indicated by the arrows in figure 5, the easy- axis flux of the write top pole layer 42 and the merged or combined write bottom pole- read top shield layer 34 pass through the edge shorting components 52, thus eliminating the edge curling domains, which are a feature of the conventional arrangement. Figure 6 is a plan view of the embodiment with the write top pole 42 not shown. Figure 7 is representation of a view of the embodiment as presented to the air bearing surface (ABS).

The manufacturing process of the first embodiment is significantly more simple than that of conventional laminate layers. In particular, a chemical etch process may be used for the patterning of the magnetic material rather than the conventional ion mill process.

Moreover, the write top pole 42 and the merged or combined write bottom pole-read top shield 34 may be patterned in a series of steps, thereby obtaining thick magnetic layers by means of a series of thin photo-resist layers. Thus, there is a reduction in the fringing and necking effects on small components, for example the write top pole, caused by standing wave interference. Consequently, components may be reduced in size to accommodate higher density data storage. In addition, the manufacturing method is considerably more tolerant of variations in the lapping process.

A second embodiment of the present invention is shown in figure 8. The second embodiment is the same as the first embodiment except that the edge shorting components 52 extend substantially around the periphery of the write top pole and the merged or combined write bottom pole-read top shield. Figure 9 is representation of a view of the second embodiment as presented to the air bearing surface (ABS). The embodiment is manufactured by the same process as that for the first embodiment except that the patterning process is modified to produce the required structure. This embodiment eliminates the corrosion problems associated with the exposure of reactive laminate layers, which are used in the write gap, at the air bearing surface. Thus, a more comprehensive range of materials may be used.

The magnetic layers, i. e. the write top pole 42, the merged or combined write bottom pole-read top shield 34, the edge shorting components 52 and the bottom shield 32, may be of different, or different compositions of, magnetic materials. In particular, the merged or combined write bottom pole-read top shield and the bottom shield may be made of different magnetic materials. Hence, the structural hardness of each layer may be selected to provide for varying rates of wear for each layer during use of the head assembly. Thus, intrinsic slots may be formed in the contour of a tape drive head assembly. Furthermore, by making an appropriate choice of layer thickness and material, for example DLC or refractory metal, and by reducing the head assembly to media spacing the pole wear rates may be minimised. Moreover, the effects of saturation may be reduced by making the shield layer adjacent to the write component, i. e. the merged or combined write bottom pole -read top shield 34, from a material with a higher moment than that of the bottom shield 32. Thus, the assembly head field gradient is increased and the signal to noise ratio of written data transitions are improved. Figure 10 illustrates an arrangement for enhancing the head assembly contours by means of accelerated wear of the laminations in the assembly structure. The laminated layers of the head assembly, namely laminated shields 62, the write gap 64 and the read gap 66 can be preferentially worn by the aforementioned selection of materials of different hardness and by passing a tape 68 with a machined contour over the head assembly.

There are many benefits of the present invention over conventional merged head assemblies both in manufacture and in use.

The domain wall density in the shields is reduced. Thus, the possibility of shield domain walls overlapping and causing interaction with the sensor region or the read element is reduced.

Furthermore, the magnetic stability of the head is much improved, a feature which is especially useful at high media track densities. In particular, there is a reduction in the coupling between adjacent shields in the assembly and a reduction in write component cross- talk by virtue of a reduction in stray flux in the assembly, which in turn reduces the magnetostatic coupling. In addition, the improved magnetic stability is achieved by the formation of a closed magnetic system for each shield, which reduces interaction between and among shields. In conventional head assemblies interaction between shields can be a problem. In particular, interference from the shared pole lower shield to the lower shield magnetic alignment during write operations may occur. The closed magnetic system of the present invention also constitutes a magnetically stable system, allowing the shields to be subject to large applied fields during fabrication and operation. Thus, the flexibility and ease of processing of the head can be achieved and the long-term reliability of the head is significantly improved.

Moreover, the high frequency permeability performance is improved on account of the reduction in the eddy current losses in the head assembly. Thus, there is a greater efficiency in the screening of stray flux.

The aforegoing description has been given by way of example only and it will be appreciated by a person skilled in the art that modifications can be made without departing from the scope of the present invention.