Thermally stable spin valve films with synthetic antiferromagnet pinned by NiMn for recording heads beyond 20 Gbit/in.2

Abstract

The thermal stability of spin valve films with synthetic antiferromagnet (SAF) pinned by antiferromagnetic IrMn, NiO, and NiMn layers were studied. The SAF layer enhances the thermal stability in general; however, the blocking temperature (and the blocking temperature distribution) of the antiferromagnet is still important for the magnetic rigidity of the pinned layer. Once the temperature reaches the blocking temperature the SAF layer can go into either the spin flip or flop state, depending upon the magnetic moment ratio of the reference layer and pinned layers. The GMR linear head response can be distorted for nonlinearity. The NiMn pinned SAF structure shows magnetic and thermal stability which makes it practical for the real products. A high GMR of 11% can be obtained in both bottom and top NiMn SAF spin valves by advanced processes. Recording heads were built using such stacks which demonstrated recording areal density of 20 Gbit/in.2 and beyond.