PSEUDOCRYSTALLINE MODEL OF THE MAGNETIC-ANISOTROPY IN AMORPHOUS RARE-EARTH TRANSITION-METAL THIN-FILMS

A pseudocrystalline model is proposed to explain the occurrence of perpendicular anisotropy in amorphous rare-earth-transition metal (R-T) thin films. It is based on the central hypothesis that during layer-by-layer growth small planar hexagonal units are formed defining on average a preferential axis perpendicular to the film plane. The units are similar in structure to relaxed crystalline ones and are estimated to typically comprise six rare-earth atoms. They are regarded as an idealized model of the short-range order and are consistent with the known nearest-neighbor R-T and T-T coordination numbers in the amorphous state. This model is able to explain the known experimental results concerning the influence of composition, substrate temperature, annealing, and bombardment effects during sputter deposition on the magnetic anisotropy of thin amorphous rare-earth-transition-metal films of the system (Nd, Th, Dy) (Fe, Co), as well as the destruction of this anisotropy by additives.