Effect of Cu surface segregation on the exchange coupling field of NiFe/FeMn bilayers

The NiFe/FeMn bilayers with different buffer layers (Ta or Ta/Cu) were prepared by magnetron sputtering. Results show that the exchange coupling field of NiFe/FeMn films with Ta buffer is higher than that of the films with Ta/ Cu buffer. We analysed the reasons by investigating the crystallographic texture, surface roughness and surface segregation of both films, respectively. We found that the decrease of the exchange coupling fields of NiFe/FeMn films with Ta/ Cu buffer layers was mainly caused by the Cu surface segregation on NiFe surface.