Influence of the interface on the magnetic properties of ferromagnetic ultrathin films with various adjacent copper thicknesses

Abstract

The interface and magnetic properties of two series of films with Ta(5 nm)/Fe<inf>20</inf>Ni<inf>80</inf>Nd<inf>0.017</inf>(3 nm)/Cu(t nm) and Ta(5 nm)/Cu(t nm)/Fe<inf>50</inf>Co<inf>50</inf>Gd<inf>0.07</inf>(3 nm)/Cu(2 nm) structures have been investigated by atomic force microscopy, vibrating sample magnetometer, and ferromagnetic resonance (FMR). The roughness of all films increases with increasing copper thickness, which causes the different grain sizes in the surface of films. The coercivity of FeCo-Gd films increases with increasing thickness of inserted Cu layer while decreases with increasing thickness of Cu capping layer for FeNi-Nd films. FMR linewidth exhibits huge dependence on the thickness of inserted Cu layer for FeCo-Gd films, increasing from 2270 to 3680 Oe, which comes from the additional contribution of effect of the two-magnon scattering. And the thickness of Cu capping layer shows also an influence on FMR linewidth of FeNi-Nd films, increasing from 190 to 320 Oe, which mainly comes from intrinsic FMR linewidth and plus minor inhomogeneous broadening. All of these extrinsic linewidth broadening are related to the interface roughness. © 2014 AIP Publishing LLC.