Granted Patent B1

US 9,293,160 · App. 14/616,621 · Granted Mar 22, 2016

Abstract

Claims (27)

1. A system, comprising:

a sensor having:

a first free layer;

a second free layer above the first free layer in a track direction, the free layers exhibiting an anomalous Hall effect;

a nonmagnetic spacer layer between the first free layer and the second free layer;

a magnetic underlayer below the first free layer in the track direction for biasing a magnetic orientation of the first free layer in a first magnetic orientation;

a magnetic overlayer above the second free layer in the track direction for biasing a magnetic orientation of the second free layer in a second magnetic orientation antiparallel to the first magnetic orientation;

a lower nonmagnetic spacer layer between the magnetic underlayer and the first free layer; and

an upper nonmagnetic spacer layer between the magnetic overlayer and the second free layer;

a first set of electrodes configured to pass a current through the first free layer and the second free layer in a first direction; and

at least one second electrode configured to allow measurement of a Hall voltage of the first free layer and the second free layer in a second direction orthogonal to the first direction;

wherein a magnetic orientation of the magnetic overlayer is oriented antiparallel to the magnetic orientation of the second free layer, and a magnetic orientation of the magnetic underlayer is oriented antiparallel to the magnetic orientation of the first free layer;

wherein the sensor is configured such that the Hall voltage is substantially 0 volts when the sensor is at a quiescent state.

2. The system as recited in claim 1 , comprising:

a first shield; and

a second shield.

3. The system as recited in claim 1 , wherein the first direction is parallel to a media-facing surface of the first free layer, such that the first set of electrodes are configured to pass the current through edges of the free layers in a direction parallel to the media-facing surface.

4. The system as recited in claim 3 , wherein the first direction is in a track width direction.

5. The system as recited in claim 3 , wherein the first direction is in a track direction.

6. A magnetic data storage system, comprising:

at least one of the sensor as recited in claim 1 ;

a magnetic medium;

a drive mechanism for passing the magnetic medium over the at least one sensor; and

a controller electrically coupled to the at least one sensor for controlling operation of the at least one sensor.

7. The system as recited in claim 1 , wherein a magnetic orientation of the first free layer is nominally antiparallel with a magnetic orientation of the second free layer.

8. The system as recited in claim 1 , wherein the sensor outputs a positive Hall voltage upon influence of an external magnetic field oriented in a third direction orthogonal to a media-facing surface of the sensor, and a negative Hall voltage upon influence of an external magnetic field oriented in a fourth direction antiparallel to the third direction.

9. The system as recited in claim 1 , wherein the first free layer comprises a substantially identical composition as the second free layer, and each of the first free layer and the second free layer include manganese and at least one of iron, cobalt, nickel, platinum, boron, bismuth, and a rare earth element.

Assignments (6)