Preamplifier bias mode to re-initialize a GMR head after losing initialization
AssigneeInternational Business Machines Corporation
InventorsPaul Wingshing Chung, John Thomas Contreras, Klaas Berend Klaassen, Calvin Shizuo Nomura
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Abstract
A method and apparatus for re-initializing a GMR head after losing initialization is disclosed. The invention may use a voltage controlled waveform, which allows the current to vary with the resistance of the GMR head. Furthermore, according to a further aspect of the invention a stack of GMR heads may be reinitialized having the same orientation to preclude inversion of the reset magnetic fields on half of the heads. In addition, improvements in re-initializing GMR heads is provided by implementing wave shaping. The invention can also provide re-initialization of GMR heads at different points in the manufacturing process.
Claims17
A method for establishing a predetermined magnetic orientation of a GMR sensor, comprising the steps of:
- applying a first external magnetic field to the GMR sensor, the first external magnetic field having a first orientation relative to the GMR sensor;
- during application of the first external magnetic field, directing an electrical voltage waveform across the GMR sensor in a first direction, said voltage waveform ending at a first time;
- and
- after the first time, removing the first external magnetic field.
A method for re-establishing a predetermined magnetic orientation of GMR sensors in a stack, comprising the steps of:
- applying a first external magnetic field to the GMR sensors from a magnetic field source, the first external magnetic field having a first orientation relative to the GMR sensor;
- during application of the first external magnetic field, biasing GMR sensors facing a first direction with a first electrical waveform, said first electrical waveform ending at a first time;
- after the first time, reversing the polarity of the magnetic field to apply a second magnetic field having a second, opposite orientation relative to the GMR sensors;
- during application of the second magnetic field, biasing the GMR sensors facing a second direction with a second electrical waveform, said second electrical waveform ending at a second time;
- and
- after the second time, removing the second external magnetic field.
A method for establishing a predetermined magnetic orientation of a GMR sensor, comprising the step of applying an electrical voltage waveform across the GMR sensor in a first direction, said voltage waveform ending at a first time, the voltage waveform having a first amplitude for raising the GMR sensor above a blocking temperature and a second amplitude for setting the magnetic orientation of the GMR sensor.
Dependencies are inferred from the claim text.