Spin-valve magnetoresistive Sensor including a first antiferromagnetic layer for increasing a coercive force and a second antiferromagnetic layer for imposing a longitudinal bias

A spin-valve magnetoresistive sensor comprising:

• (a) at least two ferromagnetic layers layered with a non-magnetic layer sandwiched therebetween, said at least two ferromagnetic layers including a first and a second ferromagnetic layers, said second ferromagnetic layer including a magnetic sensing region substantially equal in longitudinal length to a track width;
• (b) a first antiferromagnetic layer layered adjacent to one of the layer planes of said first ferromagnetic layer for increasing the coercive force of said first ferromagnetic layer to pin the magnetization direction of said first ferromagnetic layer;
• (c) a pair of second antiferromagnetic layers respectively positioned adjacent to the longitudinal ends of said second ferromagnetic layer;
• (d) a pair of third ferromagnetic layers respectively layered adjacent to said pair of second antiferromagnetic layers for inducing magnetic anisotropy to pin the magnetization directions of said pair of third ferromagnetic layers in a direction perpendicular to the pinned magnetization direction of said first ferromagnetic layer, so that the magnetic field of said third magnetic layer having the pinned magnetization direction imposes a longitudinal bias on the magnetic sensing region in said second ferromagnetic layer to stabilize magnetic domains in said magnetic sensing region and orient the magnetization direction of said magnetic sensing region perpendicular to the pinned magnetization direction of said first ferromagnetic layer in the absence of any external magnetic field, whereas, in the presence of an external magnetic field, permitting the magnetization direction of said magnetic sensing region to freely rotate to the direction of said external magnetic field, wherein
• (e) said first antiferromagnetic layer is made of α-Fe2O3, and
• (f) said pair of second antiferromagnetic layers are made of an X—Mn system alloy where said X is made of at least one metal selected from the group consisting of Pt, Pd, Ir, Ru or Rh.