Structure and magnetic properties of ultrathin iron films deposited on the CoGa(100) surface

Abstract

Epitaxial bcc \ensuremath{\alpha}-Fe(100) films are grown on the (100) surface of a CoGa crystal. The misfit between the Fe and the CoGa lattices is very small (0.5%). Both, at room temperature and at 550 K layer by layer growth is found with thermal energy helium atom scattering (TEAS). The TEAS experiments show that iron films grown at 550 K on reconstructed $c(4\ifmmode\times\else\texttimes\fi{}2)$ CoGa(100) are smooth. The iron films are stable up to a temperature of 650 K. The magnetic properties of the Fe films are investigated with the magneto-optical Kerr effect. Fe films with a thickness in excess of 1.1--1.3 ML are ferromagnetic at 300 K, with the easy axis for magnetization oriented parallel to the surface. It is found that the coercive field ${H}_{c}$ is sensitive to the order of the film. Upon annealing at 550--600 K subsequent to deposition, the coercive field, measured around room temperature, increases. The ordering of the film appeared to have no effect on the remanent magnetization. For a 1.7 ML Fe film a Curie temperature of 525 K is measured. At higher coverage the Curie temperature increases to above 600 K. The coercive field ${H}_{c}$ is found to approach zero at a 50--100 K lower temperature.