Brillouin light scattering from ultrathin iron films (abstract)

Abstract

The thickness dependence of the magnetization, magnetic anisotropy, coercive forces, and g factors of an ultrathin Fe film are studied by Brillouin scattering and magneto-optic Kerr effect at room temperature. The wedge Fe film was fabricated on a Ag buffer with GaAs[100] substrate by means of molecular-beam epitaxy technique. The epitaxial growth and crystalline quality of the specimen structures were controlled by reflection high-energy electron diffraction, spot profile analysis-low energy electron diffraction (SPA-LEED), and Auger electron spectroscopy techniques. The measured magnetization and thickness dependence [1.5–16 monolayer (ML)] are compared with the theoretical predictions. Two magnetic order phases are identified, paramagnetic for 1.5 ML and magnetic for 2 ML and thicker film. It is found that g factor is 7% smaller in 1.5 ML film than that in the bulk. A nearly linear thickness dependence of coercive force in this film is observed. The establishing of the bulk in-plane anisotropy shows similar behavior as that of the magnetization, but with a delay in thickness. No apparent perpendicular magnetic anisotropy is observed at room temperature in this sample, which may be related to the nearly perfect in-plane lattice matching between the sandwiched Fe layer and Ag buffer and capping layers.