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Browse Prior Art Database

Enhanced Sensitivity for Current Biased Spin Valve Sensor

IP.com Disclosure Number: IPCOM000117783D
Original Publication Date: 1996-Jun-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Gill, HS: AUTHOR [+2]

Abstract

Conventional design of spin valve sensor utilizes a NiFe/Cu/NiFe arrangement in which one of the NiFe layers is pinned using external applied magnetic field. Another design utilizes the same arrangement with magnetization of both layers free to move under applied magnetic field. In this alternative design, the spin valve sensor is oriented so that the magnetic easy axis of NiFe layers is parallel to the air bearing surface and sense current flows perpendicular to the air bearing surface.

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Enhanced Sensitivity for Current Biased Spin Valve Sensor

      Conventional design of spin valve sensor utilizes a
NiFe/Cu/NiFe arrangement in which one of the NiFe layers is pinned
using external applied magnetic field.  Another design utilizes the
same arrangement with magnetization of both layers free to move under
applied magnetic field.  In this alternative design, the spin valve
sensor is oriented so that the magnetic easy axis of NiFe layers is
parallel to the air bearing surface and sense current flows
perpendicular to the air bearing surface.  Following earlier work (*)
on sensors of this type, it can be shown that the effective magnetic
anisotropy of shielded NiFe/Cu/NiFe spin valve sensor is given by the
following equation:
  Hk (effective) = Hk (intrinsic) - 2Hfc + Hi/cossup 3 theta
  Hk (intrinsic): magnetic anisotropy of flat film NiFe
  Hfc: ferromagnetic coupling field between NiFe layers across Cu
        spacer
  Hi: magnetic field from sense current
  theta: Angle between the magnetization of each NiFe layer and axis
perpendicular to the air bearing surface

      Since the contribution of the coupling field Hfc is subtracted
from the contribution of Hk and Hi/cossup 3 theta, a very low
effective anisotropy is possible.  This implies that it is possible
to construct a very sensitive spin valve sensor using this approach.
For example, current density of 2.5x10sup7A/cm2 implies about 2.5 mA
current through a 1 um wide (Track width)...