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Browse Prior Art Database

Magnetically Shielded Twin-Track Magnetic Read Head Structure

IP.com Disclosure Number: IPCOM000047904D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 4 page(s) / 61K

Publishing Venue

IBM

Related People

Vinal, AW: AUTHOR

Abstract

This disclosure describes improved shielding for a magnetic read head used in a twin-track recording/read-back technique. Prior shielded magnetic read head structures are known; for example, U. S. Patent 3,921,217 shows one such example. Several problems exist with the prior devices, however, in that an isolated one bit may not be sensed. Other difficulties exist as well and will be described in further detail below. Fig. 1 illustrates a simplified cross-sectional view of a typical thin film read head using a magnetoresistive (MR) sensor element. A magnetic medium 1 magnetized either longitudinally, as shown by the magnetic vectors, or vertically moves with a velocity V towards the left in Fig. 1. At some height h above its surface, the demagnetizing field present at the magnetic transition areas in the tape die out to zero.

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Magnetically Shielded Twin-Track Magnetic Read Head Structure

This disclosure describes improved shielding for a magnetic read head used in a twin-track recording/read-back technique. Prior shielded magnetic read head structures are known; for example, U. S. Patent 3,921,217 shows one such example. Several problems exist with the prior devices, however, in that an isolated one bit may not be sensed. Other difficulties exist as well and will be described in further detail below. Fig. 1 illustrates a simplified cross-sectional view of a typical thin film read head using a magnetoresistive (MR) sensor element. A magnetic medium 1 magnetized either longitudinally, as shown by the magnetic vectors, or vertically moves with a velocity V towards the left in Fig.
1. At some height h above its surface, the demagnetizing field present at the magnetic transition areas in the tape die out to zero. This presents a problem for a magnetic read head using either a direct sensor placed within the field or a magnetically conductive coupling element to couple sensed fields to the sensor. In the figure, a coupling element of nickel-iron alloy 4 is exposed at the surface 7 of the read head. The MR element 2 is in contact with the nickel-iron element 4 and with another nickel-iron element 6 which is integral with the nickel-iron side shields 5. A magnetic flux circuit from 4 through 2 and 6 and out through 5 thus exists. Unfortunately, flying heights of typical read heads and the relatively great length of the element 2 dictate that only a small portion of the MR element will actually "see" the magnetic transition fields at the boundaries of the magnetized area in the magnetic medium 1. Of course, if the MR element is brought down into very close proximity with the magnetic medium, more of the element would be subject to the flux field. It is the purpose of the design in Fig. 1 to couple as much as possible of the flux field through the magnetically permeable coupling leg 4 and into the MR element 2 and through its connection 6 out through the coupling leg/shield 5 generally along the position marked by arrow 8. With normal flying heights above the magnetic medium 1, the end of the nickel-iron element 4 will see part of the flux fields from adjacent bit transitions identified by arrows 11 in Fig. 1 and thus the shields 5 are not effective to completely decouple the effects of adjacent transitions. However, the shields do intercept some of the flux fields from transitions 9 and 10 and couple them back to the medium without allowing them to enter the sensor 2. This is the purpose of the shields primarily but the leftmost leg 5 of the shield is also a coupling leg to complete the magnetic circuit through the sensor 2 and the magnetic image pole, for the transition 9 will be produced generally in the region of the arrow 8 in Fig. 1 to complete the circuit through elements 5, 6, 2 and 4. It has been found that practical read heads of this style eliminate th...