Effect of Ta and Ta/Cu buffers on the exchange bias field of NiFe/FeMn bilayers

The NiFe/FeMn bilayers with different buffer layers (Ta or Ta/Cu) and Ta co ver layers were prepared by magnetron sputtering. The results showed that t he exchange bias field of NiFe/FeMn films with the Ta buffer was higher tha n that of the films with the Ta/Cu buffer. We investigated the crystallogra phic, texture, surface roughness and surface segregation, and demonstrated that the decrease of the exchange coupling field was caused by the Cu surfa ce segregation in NiFe/FeMn films with Ta/Cu buffer layers.