GROWTH OF ULTRATHIN FE FILMS ON GE(100) - STRUCTURE AND MAGNETIC-PROPERTIES

The structure and magnetic properties of ultrathin Fe films grown on G e(100) at room temperature have been studied by low-energy electron di ffraction, Auger electron spectroscopy (AES), angle-resolved AES, and in situ magneto-optical Ken effect (MOKE) measurements. Fe initially g rows on Ge(100) in a disordered fashion, with local order commencing a round 4 ML. The film grows with a bcc structure for thicknesses greate r than 7 ML. Our data are consistent with 6% Ge intermixed in the film s. Significant intermixing starts at about 160 degrees C, with rapid d iffusion of Fe into the bulk occurring at temperatures higher than 400 degrees C. A single-loop to stepped-loop to single-loop sequence of f erromagnetic loops was observed by MOKE measurements. Hysteresis loop simulations were performed based on the coherent model, the results su ggesting that strong in-plane uniaxial anisotropy exists in these film s, especially for very thin films. The sequence of loops is due to the increase of the ratio between the cubic anisotropy and the uniaxial a nisotropy as the film thickness increases.