Fe-Dy Nanogranular Thin Films: Investigation of Structural, Microstructural and Magnetic Properties

A series of Fe₁₀₀− _x Dy _x thin films with the concentration range x = 6 to 35 were fabricated by dc magnetron sputtering process. X-ray diffraction and TEM studies revealed that films have separate Fe and Dy nanograins and that there is no intermixing of Fe and Dy thus forming nanogranular films. This unmixed behaviour in our thin films is very different from the bulk Fe-Dy alloys where several stoichiometric compounds can be formed. Magnetic properties of the films have been systematically studied. The contribution to the total magnetization is due to the Fe grains and the Dy grains are paramagnetic down to 4 K. The saturation magnetization of all the samples is significantly lower than that of bulk Fe due to the existence of superparamagnetic Fe grains. Upon increasing x, the in-plane magnetic anisotropy is found to decrease and the samples become isotropic. The zero field cooled and field cooled magnetization measurements also confirmed the presence of the superparamagnetic Fe grains.