Structural and magnetic properties of Fe films grown on GaAS

A study is presented of magnetic and structural properties of thin Fe films deposited on (111) GaAs substrates for thicknesses ranging from 65 to 120 nm. The films grown by ion-beam-sputtering exhibit both bcc phase and ferromagnetic structure. Transmission electron microscopy has allowed to determine the morphological growth stages and the grain size of the films. Both vibrating sample magnetometry and Mössbauer effect measurements show that the magnetic moments are lying in the film plane for every film. The average magnetization and $^{57}$Fe hyperfine field decrease with decreasing thickness which indicates the existence of two iron sites. An in-plane uniaxial anisotropy is found for the 65 nm thick film. Finally at film thickness approaching 120 nm, the film assumes the character of bulk $\alpha$-Fe.