Structural and magnetic properties of compositionally modulated Nd-Co thin films

In order to investigate the origin of the perpendicular magnetic anisotropy in rare earth - transition metal films, a series of compositionally modulated films (CMF´s) which consist of alternate layers of Nd and Co has been prepared by UHV evaporation. The Nd and Co layers had equal thickness in each sample; layer thicknesses varied from 12 to 32Å. The samples are deposited on glass substrates which are kept at room temperature in ultra-high vacuum (10^-9Torr). The RHEED patterns observed in situ and X-ray diffraction patterns show that all samples have compositionally modulated structures, although the interface region is not crystalline. These films have a perpendicular magnetic anisotropy component, which increases with decreasing the compositional modulation period. From the temperature dependence of magnetization and NMR spectra at 4.2K, it is thought that the perpendicular anisotropy energy is induced from Nd atoms which are adjacent to Co atoms in the vicinity of the interface.