Influence of metal spacer on the properties and microstructure of multilayer films and analyses

Ta/NiFe/nonmagnetic metal spacer/FeMn/Ta films were prepared by magnetron sputtering. The dependence of the exchange coupling field (Hex) between the FeMn and NiFe layers on the thickness of a nonmagnetic metal spacer layers was investigated systematically. The results show that Hex decreases rapidly with increasing thicknesses of the Bi and Ag spacer layers. It decreases gradually, however, with an increase in the thickness of the Cu spacer layer. We found empirically that Hex corresponds to the lattice match between spacer layer atoms and NiFe layer atoms. However, the results of X-ray photoelectron spectroscopy show that when a small amount of Bi atoms are deposited on the NiFe/FeMn interface, they migrate to the FeMn layer surface and hardly influence Hex.