US 8,711,524 B2Granted

Patterned MR device with controlled shape anisotropy

AssigneeHeadway Technologies, Inc.

InventorsYuchen Zhou, Yimin Guo

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Abstract

A magnetic sensor with increased sensitivity, lower noise, and improved frequency response is described. The sensor's free layer is ribbon shaped and is closely flanked at each long edge by a ribbon of magnetically soft, high permeability material. This side pattern absorbs external field flux, concentrating it to flow into the sensor's edges to promote larger MR sensor magnetization rotation.

Claims3

Dependent claims

A method of fabricating a magnetic sensor, comprising:

depositing a layer of magneto-resistive (MR) device material;
patterning said device layer to form a MR stripe having a bottom surface, a top layer that is a magnetically free layer having a first top surface, an aspect ratio of at least 5, a pair of opposing first edges that are equidistant from a center plane that bisects the MR stripe in a lengthwise direction, and a first thickness;
depositing and patterning a layer of soft magnetic material to form a pair of flux absorbing stripes each having a second edge facing the center plane, a second top surface, and a second thickness;
positioning said flux absorbing stripes so that the second edge of a first flux absorbing stripe is offset from one of the opposing first edges of the free layer along a second direction that is orthogonal to the center plane, and the second edge of a second flux absorbing stripe is offset from another of the opposing first edges of the free layer in a direction opposite to the second direction, with no part of said MR stripe being coplanar with any part of said flux absorbing stripes along any plane aligned perpendicular to the center plane, and with adjacent pairs of said first and second edges running parallel to each other, said adjacent edge pairs being separated from one another by a distance that is no greater than twice the larger of said first and second thicknesses, as measured from a one of the opposing first edges in a direction parallel to said free layer top surface;
selecting values for said first and second thicknesses so that, at all times, a product of said soft magnetic stripe's magnetization times said second thickness is greater than a product of said free layer's magnetization times said first thickness;
and
thereby ensuring that said free layer undergoes uniform rotation when its direction of magnetization is reversed, that said free layer primarily comprises a single magnetic domain, and that field concentration and demagnetization cancellation by neighboring soft magnetic patterns are not limited by said free layer's properties whereby said free layer can be independently optimized to increase sensitivity for said MR sensor.

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Dependencies are inferred from the claim text.

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Abstract

A method of fabricating a magnetic sensor, comprising:

depositing a layer of magneto-resistive (MR) device material;
patterning said device layer to form a MR stripe having a bottom surface, a top layer that is a magnetically free layer having a first top surface, an aspect ratio of at least 5, a pair of opposing first edges that are equidistant from a center plane that bisects the MR stripe in a lengthwise direction, and a first thickness;
depositing and patterning a layer of soft magnetic material to form a pair of flux absorbing stripes each having a second edge facing the center plane, a second top surface, and a second thickness;
positioning said flux absorbing stripes so that the second edge of a first flux absorbing stripe is offset from one of the opposing first edges of the free layer along a second direction that is orthogonal to the center plane, and the second edge of a second flux absorbing stripe is offset from another of the opposing first edges of the free layer in a direction opposite to the second direction, with no part of said MR stripe being coplanar with any part of said flux absorbing stripes along any plane aligned perpendicular to the center plane, and with adjacent pairs of said first and second edges running parallel to each other, said adjacent edge pairs being separated from one another by a distance that is no greater than twice the larger of said first and second thicknesses, as measured from a one of the opposing first edges in a direction parallel to said free layer top surface;
selecting values for said first and second thicknesses so that, at all times, a product of said soft magnetic stripe's magnetization times said second thickness is greater than a product of said free layer's magnetization times said first thickness;
and
thereby ensuring that said free layer undergoes uniform rotation when its direction of magnetization is reversed, that said free layer primarily comprises a single magnetic domain, and that field concentration and demagnetization cancellation by neighboring soft magnetic patterns are not limited by said free layer's properties whereby said free layer can be independently optimized to increase sensitivity for said MR sensor.

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