Shield design for stable magnetoresistive head

#The field of invention relates to direct access data storage, generally. More specifically, the invention relates to compensating for the effect of image poles within a magnetic head.

#Hardware systems often include memory storage devices having media on which data can be written to and read from. A direct access storage device (DASD or disk drive) incorporating rotating magnetic disks are commonly used for storing data in magnetic form. Magnetic heads, when writing data, record concentric, radially spaced information tracks on the rotating disks.

#Magnetic heads also typically include read sensors that read data from the tracks on the disk surfaces. In high capacity disk drives, magnetoresistive (MR) read sensors, the defining structure of MR heads, can read stored data at higher linear densities than thin film heads. An MR head detects the magnetic field(s) through the change in resistance of its MR sensor. The resistance of the MR sensor changes as a function of the direction of the magnetic flux that emanates from the rotating disk.

#The present invention is illustrated by way of example, and not limitation, in the Figures of the accompanying drawings in which:

#FIG. 1 shows a prior art AP sensor.

#FIG. 2a shows the track width and stripe height associated with the prior art AP sensor of FIG. 1.

#A multilayer structure is disclosed having a magneto resistive free layer. The multilayer structure is between a pair of shields and the shields are separated by at least two spacings. A first of the spacings is at least the length of the multilayer structure. A second of the spacings is greater than the first spacing.

#These and other embodiments of the present invention may be realized in accordance with the following teachings and it should be evident that various modifications and changes may be made in the following teachings without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense and the invention measured only in terms of the claims.

#Referring to FIG. 2a, recall from the background that a problem with sensors such as sensor 200 is the stability of the free layer 203a as track dimensions continually narrow. For example, in some cases as track widths 291 fall below 0.50 μm, the direction that the free layer 203a magnetization points toward can “jump” between the +x direction and the −x direction (and vice versa) as the sensor passes over a disk (lying in the xy plane) having flux lines emanating/terminating in the + and − z directions. This jumping activity is an undesireable instability FIG. 2a does not show the disk or its flux lines for simplicity; however briefly looking at FIG. 3, one can see a disk 371 and its associated flux lines 370.