Antiferromagnetic and hard-magnetic stabilization schemes for magnetoresistive sensors

Antiferromagnetic Ni-Mn and hard-magnetic CoPt-Cr stabilization schemes for magnetoresistive (MR) sensors are evaluated in this paper. Magnetic properties of Ni-Fe(bottom)/Ni-Mn(top), Ni-Mn/Ni-Fe, Co-Pt-Cr, Ni-Fe/Co-Pt-Cr and Co-Pt-Cr/Ni-Fe films used in various types of MR sensors are characterized, and the read performance of two types of MR sensors, one overlaid with a Ni-Mn film in tail regions and the other abutted with a Co-Pt-Cr film, is then studied. In the Ni-Mn stabilization scheme, the unidirectional anisotropy field of the Ni-Fe/Ni-Mn films increases when the MR sensor is thinner, and the MR responses are quiet and stable. In the Co-Pt-Cr stabilization scheme, the remanence magnetic moment and coercivity of the Co-Pt-Cr film decrease when the film is thinner, and the MR responses are quiet and stable when the magnetic moment of the Co-Pt-Cr film is higher than that of the MR film. This magnetic moment cannot be very high to prevent the reduction of sensor sensitivity and effective readwidth. To select a suitable stabilization scheme for thinner MR sensors, simplicity in sensor magnetics and fabrication should also be considered.