The NiFe/FeMn bilayers with different buffer layers (Th or Ta/Cu) were prep
ared by magnetron sputtering Results show that the exchange coupling field
of NiFe/FeMn films with Th buffer is higher than that of the films with Ta/
Cu buffer. We analysed the reasons by investigating the crystallographic te
xture, surface roughness and surface segregation of both films, respectivel
y. 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 segrega
tion on NiFe surface.