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Magneto-resistive Reading Element

IP.com Disclosure Number: IPCOM000121281D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 93K

Publishing Venue

IBM

Related People

Pomerantz, M: AUTHOR [+4]

Abstract

A technique is described whereby a magneto-resistive reading element, as used in sensing magnetic information, is structured in such a way so as to provide flexibility in the orientation of magnetic polarization sensing material.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Magneto-resistive Reading Element

      A technique is described whereby a magneto-resistive
reading element, as used in sensing magnetic information, is
structured in such a way so as to provide flexibility in the
orientation of magnetic polarization sensing material.

      In prior art, the sensing of magnetic information (bits),
utilizing ferro-magnetic film magneto-resistive material, the
magnetization (M), as shown in Fig. 1, is caused to orient in the
plane of the film at approximately 45o, in relation to the direction
in which the bit passes. When the bit passes under the sensor, the
direction of magnetism changes, causing a change in the electrical
resistance (R) of the sensor.  The measurement of R is then used to
detect the passage of the bit.  Methods of holding the magnetic
material at 45o used in prior art have presented orientation
problems.  The concept described herein structures the element so
that the magnetization (M) is not restricted to a 45o angle, but can
be oriented in any desired angle.

      The magneto-resistive element is constructed with layers of
films, as shown in the cross-section of Fig. 2. Non-magnetic
substrate 10 is corrugated to a specific depth and length.  Magnetic
film 11 has, as its essential property, permanently magnetized with
M1 directed across the corrugations.  The magnetic coercivity and the
remanence of magnetic film 11 are large enough to enable the film to
be a single domain, with M1 uniform in the plane.  Non-magnetic film
12 electrically insulates magnetic film 13 from magnetic film 11.
Magnetic film 13 has a specific thickness (a), whereby its
magnetization M2 is orientable and used for magneto-resistive
sensing.

      In the operation of the device, magnetization M1 acts to align
the magnetization of M2 due to the dipole magnetic fields emanating
from magnetic film 11.  The fields arise only because of the
corrugations.  Planar films would have no such coupling if the
planarity were perfect.  By adjustment of the preparation of the
magnitudes of M1, M2 and the parameters of the corrugations,...