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Contiguous Hard Bias Optimization for Magneto-Resistive Head

IP.com Disclosure Number: IPCOM000118156D
Original Publication Date: 1996-Oct-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Gill, HS: AUTHOR

Abstract

The bias angle of the Magneto-Resistive (MR) sensor and, therefore, the asymmetry of the readback signal is influenced by head geometry and materials. One of the parameters which impacts the bias point is the magnetic thickness = (remanent magnetization) (thickness) of the contiguous Hard Bias material. The bias angle decreases as the Hard Bias film thickness increases to the point where the magnetic thickness of the sensor (including the thickness of soft bias layer) is matched to the magnetic thickness of the contiguous Hard Bias film. Beyond this thickness, since the edge region of the MR sensor is saturated, further increase in the Hard Bias magnetic thickness has negligible impact on the bias angle because of the limited extent of its magnetic field into the track region of the shielded MR sensor.

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Contiguous Hard Bias Optimization for Magneto-Resistive Head

      The bias angle of the Magneto-Resistive (MR) sensor and,
therefore, the asymmetry of the readback signal is influenced by head
geometry and materials.  One of the parameters which impacts the bias
point is the magnetic thickness = (remanent magnetization)
(thickness) of the contiguous Hard Bias material.  The bias angle
decreases as the  Hard Bias film thickness increases to the point
where the magnetic thickness of the sensor (including the thickness
of soft bias layer) is  matched to the magnetic thickness of the
contiguous Hard Bias film.  Beyond this thickness, since the edge
region of the MR sensor is  saturated, further increase in the Hard
Bias magnetic thickness has negligible impact on the bias angle
because of the limited extent of its  magnetic field into the track
region of the shielded MR sensor.

      It is possible to minimize the signal asymmetry variations by
selecting magnetic thicknesses so that the following equation is
satisfied:
  M(HB) x t(HB) > (M(MR) x t(MR) + M(SF) x t(SF))
  where M's and t's are remanent magnetization and thickness for
Hard Bias (HB) film, MR film and Soft bias Film (SF).  To overcome
process variations, left side of above equation should be selected
to be about 20% greater than the right side.

      It is also found that the sharper junction between the sensor
and the permanent magnetic material at the track edge provides a
sensor with hig...