Spin valves with high uniaxial anisotropy reference and keeper layers

DETAILED DESCRIPTION It is an object of the present invention to disclose an SV sensor structure with an enhanced pinning field in the pinned layer structure.
It is another object of the present invention to disclose an SV sensor wherein the pinning field is enhanced by uniaxial anisotropy in the pinned layer structure.
It is a further object of the present invention to disclose an SV sensor wherein the pinning field is enhanced by use of a high magnetostriction material to form the pinned layer.
It is yet another object of the present invention to disclose a keepered SV sensor configuration wherein a keeper layer is formed using a high uniaxial anisotropy material.
It is a still further object of the present invention to disclose an AP-Pinned SV sensor wherein one or both of the ferromagnetic sublayers forming the AP-pinned layer structure are made of high uniaxial anisotropy materials.
In accordance with the principles of the present invention, there is disclosed a preferred embodiment of the present invention wherein an SV sensor has a pinned layer formed of a high uniaxial anisotropy ferromagnetic material, such as Co--Fe, and a keeper layer formed of a second high uniaxial anisotropy ferromagnetic material, such as Ni--Fe--Nb.
During the fabrication process of the SV sensor, lapping induced tensile stress in the Co--Fe pinned layer having a high positive magnetostriction coefficient generates a stress-induced uniaxial anisotropy field in the pinned layer resulting in enhanced pinned layer magnetic saturation.
This uniaxial anisotropy field is capable by itself of maintaining a substantial transverse magnetic saturation of the pinned layer even at elevated temperatures.
Lapping induced tensile stress in the Ni--Fe--Nb layer having a high positive magnetostriction coefficient generates a stress-induced uniaxial anisotropy field in the keeper layer providing more uniform magnetization and therefore better flux cancellation.
The high electrical resistivity of the Ni--Fe--Nb keeper layer has the further benefit of reducing sense current shunting by the keeper layer