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SIGNAL ASYMMETRY CONTROL FOR GMR HEADS

IP.com Disclosure Number: IPCOM000013444D
Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 1 page(s) / 25K

Publishing Venue

IBM

Abstract

The asymmetry of read back signal of GMR heads depends on several parameters. The signal asymmetry is determined by the free layer magnetization angle relative to the pinned layer magnetization. Symmetric signal is achieved when freelayer magnetization angle becomes 90 degrees relative to the pinned layer magnetization. The free layer magnetization angle is influenced by the stress induced magnetic anisotropy among other things. The stress induced magnetic anisotropy varies as stripe height of the sensor varies, due to changes in mean stress level at the sensor by the stripe height change. In-addition, the demagnetization field from the pinned layer also varies with the stripe height. The head is designed to achieve opposite effects on the asymmetry by the pinned layer demagnetization field and the stress induced magnetic anisotropy as stripe height varies.

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SIGNAL ASYMMETRY CONTROL FOR GMR HEADS

   The asymmetry of read back signal of GMR heads depends on several parameters.
The signal asymmetry is determined by the free layer magnetization angle relative
to the pinned layer magnetization. Symmetric signal is achieved when freelayer
magnetization angle becomes 90 degrees relative to the pinned layer
magnetization. The free layer magnetization angle is influenced by the stress
induced magnetic anisotropy among other things. The stress induced magnetic
anisotropy varies as stripe height of the sensor varies, due to changes in mean
stress level at the sensor by the stripe height change. In-addition, the
demagnetization field from the pinned layer also varies with the stripe height.
The head is designed to achieve opposite effects on the asymmetry by the pinned
layer demagnetization field and the stress induced magnetic anisotropy as stripe
height varies.

For example, for a free layer with positive magnetostriction and net compressive
stress from the air bearing surface, more transverse magnetic anisotropy is
induced as the stripe height becomes shorter. This implies that the free layer
magnetization angle makes larger angle with the air bearing surface resulting in
increase in signal asymmetry. On the other hand, the pinned layer demagnetizing
field also increases as stripe height becomes shorter. The polarity of the pinned
layer demagnetization field or the sign of the magnetostriction can be selected
so that these two quantities have an...