Magnetic properties of Nd/Fe double layers grown on Si(111) by electron beam evaporation

In-plane ferromagnetic resonance (FMR) has been used to study the room-temperature magnetic and crystalline properties of Nd/Fe bilayers. Several samples were grown by electron beam evaporation onto Si(111) substrates, for various Fe and Nd thicknesses. The symmetry of the resonance field as a function of the azimuthal angle departs from the sixfold one expected for a (111)Fe film. The FMR data were analyzed in the framework of a phenomenological model, which takes into account firstand second-order magnetocrystalline, uniaxial and perpendicular anisotropies. Our analysis reveals that the deviation from the sixfold symmetry is due to a combined effect of an induced uniaxial in-plane anisotropy with a small misorientation of the substrate surface from the (111) plane. We suggest that the in-plane uniaxial anisotropy may originate from an arrangement of (111) terraces separated by well oriented atomic steps formed during the small miscut. The effect of the Nd overlayer is to induce a perpendicular anisotropy which is not sufficiently large to overcome the demagnetizing field and push the magnetization entirely out-of-plane.