Exchange bias affected by ion beam etching of FeMn surface in Ta/NiFe/FeMn

The exchange bias field of Ta(5)/NiFe(10)/FeMn(20) (nm) multilayer films are investigated as a function of FeMn thickness, where the FeMn layer is etched by Ar ion beam. It was found that the surface roughness is decreased by ion beam etching without the introduction of significant structural damage in the FeMn layer. Exchange bias improvement is observed even at the initiation of FeMn surface etching. The exchange field increases as the etching proceeds and shows maximum at FeMn thickness of 7 nm. The exchange bias begins to decrease with further etching and drops at the FeMn thickness of 5 nm.