SCISSOR UNIDIRECTIONAL BIASING WITH HARD BIAS STABILIZED SOFT BIAS
In one embodiment, a method for forming a sensor includes forming a first free layer, forming a barrier layer above the first free layer, forming a second free layer above the barrier layer, the first free layer, the barrier layer, and the second free layer together forming a scissor sensor stack, forming a soft bias layer behind the scissor sensor stack in an element height direction, the soft bias layer including a soft magnetic material, and forming a hard bias layer, at least a portion thereof being positioned behind the soft bias layer in the element height direction, the hard bias layer including a hard magnetic material having an initialization magnetization that is perpendicular to a media-facing surface of the sensor to provide unidirectional anisotropy to the soft bias layer.
1 . A method for forming a sensor, the method comprising:
forming a first free layer;
forming a barrier layer above the first free layer;
forming a second free layer above the barrier layer, wherein the first free layer, the barrier layer, and the second free layer together form a scissor sensor stack;
forming a soft bias layer behind the scissor sensor stack in an element height direction, the soft bias layer comprising a soft magnetic material; and
forming a hard bias layer, at least a portion thereof being positioned behind the soft bias layer in the element height direction, the hard bias layer comprising a hard magnetic material having an initialization magnetization that is perpendicular to a media-facing surface of the sensor to provide unidirectional anisotropy to the soft bias layer,
wherein at least one portion of an upper surface of the hard bias layer is positioned closer to the media-facing surface of the sensor than any portion of a lower surface of the hard bias layer, and
wherein at least one portion of a lower surface of the soft bias layer is positioned farther from the media-facing surface of the sensor than any portion of an upper surface of the soft bias layer.
2 . The method as recited in claim 1 , further comprising:
forming an upper shield above the scissor sensor stack, the upper shield being electrically coupled to and exchange isolated from the hard bias layer; and
forming a lower shield below the scissor sensor stack, the lower shield being electrically isolated from the hard bias layer.
3 . The method as recited in claim 2 , wherein at least a portion of the hard bias layer is in direct contact with a back edge of the soft bias layer, and wherein a portion of the soft bias layer extends below the hard bias layer in the element height direction and is configured to electrically isolate the hard bias layer the lower shield.
4 . The method as recited in claim 2 , further comprising forming an insulating layer between the soft bias layer and the hard bias layer and between the hard bias layer and the lower shield, the insulating layer being configured to electrically isolate the soft bias layer from the hard bias layer and the hard bias layer from the lower shield.
5 . The method as recited in claim 1 , wherein the soft bias layer has a length in the element height direction which is at least twice a width in a track width direction to form shape anisotropy perpendicular to the media-facing surface of the sensor, and wherein the scissor sensor stack has a width in the track width direction that is substantially equal to the width of the soft bias layer in the track width direction.
6 . The method as recited in claim 1 , further comprising forming a side shield on one or more sides of the scissor sensor stack in a track width direction.
7 . The method as recited in claim 1 , wherein at least a portion of the hard bias layer extends beyond sides of the scissor sensor stack and the soft bias layer in a track width direction.