Surface roughness effects on the magnetization reversal of polycrystalline Fe/Ag thin films

Fe films with thickness varying from 46 to 1750 إ have been deposited on oxidized Si substrates coated with a Ag buffer layer. The surface morphology of both the Ag buffer layer and the Fe films was investigated by atomic force microscopy. Analysis of the images shows that the surface roughness of the Fe layers is completely dominated by the surface roughness of the Ag buffer layer. Magnetization measurements revealed that the magnetic properties of the Fe films are strongly affected by the surface roughness. The change in the coercivity as a function of the film thickness depends on the ratio of the film thickness and the typical size of the height variations of the surface. When this ratio is smaller than 1, the coercivity increases with increasing film thickness. For a ratio larger than 1, the coercivity decreases monotonically with the film thickness.