Enhancement of exchange field and reduction of GMR in PtMn-based spin valves by ion irradiation

C-ion irradiation was performed on PtMn-based spin valves and the effects of ion irradiation on magnetoresistance (MR) and on the exchange field were investigated. When ion irradiation was performed prior to post-annealing, the exchange field was substantially enhanced after annealing, especially for an annealing temperature below 240 degreesC. The enhancement could be related to the formation of PtMn(C) phase, which might accelerate the formation of ordered PtMn phase and might increase the anisotropy of PtMn. Although the majority of C ions located in capping layers Ta and PtMn, small amounts of C ions may go into the interface of CoFe/Cu/CoFe, leading to a small MR. (C) 2002 American Institute of Physics.