Thermal stability of Ta-pinned spin valves

It has recently been found that large uniaxial anisotropy fields in excess of 120 kA/m (1500 Oe) can be created in thin (3-5 nm) films of Co by obliqu ely sputtered Ta underlayers. This anisotropy can be used to pin the bottom film of a spin valve while having only a modest effect on the top "free" f ilm, separated by a 2.5 nm Cu spacer layer. This article describes measurem ents of thermal stability in these Ta-pinned spin valves. Using room temper ature giant magnetoresistance (GMR) as a measure, we find that the structur e is stable under cumulative 20 min anneals at 25 degreesC intervals up to 300 degreesC; GMR decreases to zero upon further anneals up to 450 degreesC . Measurements taken at elevated temperatures reveal that GMR decreases lin early with temperature, extrapolating to zero at approximately 425 degreesC , while the anisotropy field is much less temperature dependent, remaining nearly constant up to 150 degreesC and gradually decreasing to 50% of its r oom temperature value at 325 degreesC. (C) 2001 American Institute of Physi cs.