Preamplifier bias mode to re-initialize a GMR head after losing initialization
First Claim
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1. 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.
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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.
47 Citations
17 Claims
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1. A method for establishing a predetermined magnetic orientation of a GMR sensor, comprising the steps of:
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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. - View Dependent Claims (2, 3, 4, 5)
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6. A method for re-establishing a predetermined magnetic orientation of GMR sensors in a stack, comprising the steps of:
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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. - View Dependent Claims (7, 8, 9, 10)
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- 11. 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.
Specification