System for resetting sensor magnetization in a spin valve magnet

Details System for resetting sensor magnetization in a spin valve magnet System for resetting sensor magnetization in a spin valve magnet

1996-02-26

1997-07-22

Psitos, Aristotelis M.

Dynamic magnetic information storage or retrieval

Automatic control of a recorder mechanism

Controlling the head

360113, 324252, 338 32R, G11B 5455, G11B 539

Patent

active

056508875

ABSTRACT:
Sensors based on the giant magnetoresistance effect, specifically "spin valve" (SV) magnetoresistive sensors, have applications as external magnetic field sensors and as read heads in magnetic recording systems, such as rigid disk drives. These sensors have a ferromagnetic layer whose magnetization orientation is fixed or pinned by being exchange coupled to an antiferromagnetic layer. The magnetization of the pinned layer will become misaligned and the sensor will experience an abnormal response to the field being sensed, i.e., the external magnetic field or the recorded data in the magnetic media, if an adverse event elevates the antiferromagnetic layer above its blocking temperature. A pinned layer mangetization reset system is incorporated into systems that use SV sensors. The reset system generates an electrical current waveform that is directed through the SV sensor with an initial current value sufficient to heat the antiferromagnetic layer above its blocking temperature, and a subsequent lower current value to generate a magnetic field around the pinned layer sufficient to properly orient the magnetization of the pinned layer while the antiferromagnetic layer is cooling below its blocking temperature. This process resets the magnetization of the pinned layer to its preferred orientation and returns the SV sensor response substantially back to its desired state.

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D. E. Heim et al., "Design and Operation of Spin Valve Sensors", IEEE Transactions on Magnetics, vol. 30, No. 2, Mar. 1994, pp. 316-321.

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