Growth and magnetic properties of ultrathin Fe films on Pt(1 1 1)

Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and surface magneto-optical Kerr effect (SMOKE) were used to investigate the growth mode, alloy formation, and magnetic properties of ultrathin Fe films deposited on Pt(1 1 1) surface. The growth mode of Fe films on Pt(1 1 1) at RT is at least 3 ML layer-by-layer growth before three-dimensional island growth begins. When the thickness of Fe films was 1 ML, no Kerr signal is observed at room temperature. Both the polar and longitudinal Kerr signals can be detected when the thickness of Fe films (d_Fe) is 1.5 ML. When the thickness of Fe films is higher than 1.5 ML, only the longitudinal Kerr signal can be observed. The easy axis of the magnetization is in the in-plane direction when d_Fe > 1.5 ML. After the formation of Fe-Pt surface alloy for 5 ML Fe ultrathin films on a flat Pt(1 1 1) surface, the Kerr signal and the coercivity enhance to 150% and 1100%, respectively. The formation of Fe-Pt surface alloy was confirmed by AES. The evolutions of the magnetic properties are strongly relative to the diffusion process of Fe thin films into Pt substrate.