Method for manufacturing a tunnel junction sensor with non-shunting stabilization
View Patent ↗A magnetic tunnel junction (MTJ) sensor in which the free layer longitudinal biasing elements are coupled, without insulation, to the free layer outside of the MTJ stack to provide reliable non-shunting MTJ free layer stabilization without extremely thin dielectric layers. In one embodiment, hard magnetic (HM) layers are disposed in contact with the free layer outside of and separated from the MTJ stack active region by a thick dielectric layer. In another embodiment, antiferromagnetic (AFM) bias layers are disposed in contact with the free layer outside of and separated from the MTJ stack active region by a thick dielectric layer. In other embodiments, nonconductive HM layers are disposed either in contact with the free layer outside of the MTJ stack active region and/or in abutting contact with the MTJ stack active region.
1. A method for fabricating a magnetic tunnel junction (MTJ) sensor for use in a magnetic read head having an air bearing surface (ABS), the method comprising the unordered steps of:
(a) forming a MTJ stack with an active region disposed at the ABS and having two opposite sides each disposed generally orthogonally to the ABS, including the unordered steps of:
(a.1) forming an antiferromanetic (AFM) layer,
(a.2) forming a pinned layer of ferromagnetic (FM) material in contact with the AFM layer,
(a.3) forming a free layer of FM material,
(a.4) forming a tunnel junction layer of electrically nonconductive material disposed between the pinned layer and the free layer, and
(a.5) removing all material outside of the active region from the AFM layer, the pinned layer, and the tunnel junction layer to define the two opposite sides of the active region; and
(b) forming a longitudinal bias layer outside of the active region in contact with the free layer for biasing the magnetic moment of the free layer in substantially a predetermined direction in the absence of an external magnetic field, the bias layer comprising an AFM material.
2. The method of claim 1 further comprising the step of;
(c) forming an insulating layer of electrically nonconductive material on and in contact with the free layer outside of the active region and in abutting contact with the two opposite sides of the active region.
3. The method of claim 2 wherein the longitudinal bias layer is disposed without contacting the active region.
4. The method of claim 1 wherein the longitudinal bias layer is disposed without contacting the active region.
5. The method of claim 1 , wherein a portion of the free layer extends beyond the active region, and wherein the bias layer is exchange coupled with the free layer outside of the active region.