Kinetics of thermal decay in NiMn and PtMn spin valve devices

The thermal stability of NiMn and PtMn exchange-biased spin valves is studied in fully integrated magnetic recording heads. Constant temperature and voltage are applied to simulate stress conditions, and magnetic transfer curves are measured in situ to follow the magnetization kinetics. For both types of spin valves, the amplitude of the magnetoresistance changes as the square root of time, and the lifetimes are distributed as a lognormal function. Linear scaling of the lifetime distributions strongly suggests the same mechanism in both NiMn and PtMn structures. However PtMn spin valves with a synthetic antiferromagnetic pinned layer are more stable than NiMn structures with a simple pinned layer