Thermal reliability of NiMn-based spin valves

The thermal reliability of NiMn-based top spin valve was studied at sensor temperatures between 200 and 300 °C by furnace annealing and thermal-electrical stressing. Sensor resistance was measured as a function of heating time up to 1000 h. The sensor resistance change (dR/R) vs time (t) curves showed diffusion-like characteristics. Sensor lifetime for 0.5% resistance increase was determined from the Arrhenius plot to be more than 5 years at 200 °C anneal condition. Temperature- independent linear relationship between resistance change and time was observed in both anneal and bias stress conditions in dR/R=0.2%–3% range. It suggests an interface-controlled kinetics for the sensor failure process. Comparison between the reliability results from two types of stress suggests that device degradation is accelerated by the electrical bias when at the same sensor temperature.