Structural and magnetic characterization of thin iron films on a tungsten (001) substrate

The structure and remanent magnetization of iron films of thickness up to 5 monolayers (ML), grown on a tungsten (001) substrate at room temperature, have been characterized. The iron grows pseudomorphically, monolayer-by-monolayer, up to a thickness of 2 ML. Subsequent film growth is disordered, but does not form islands until annealed. One pseudomorphic monolayer is stable upon annealing up to the desorption temperature. Magnetic hysteresis loops of the films (at room temperature) were collected in remanence, by measuring the spin polarization imparted by diffraction to an initially unpolarized electron beam. The films show in-plane ferromagnetism beginning at a thickness between 1.35 ± 0.05 and 1.50 ± 0.06 ML, and have biaxial in-plane anisotropy. The easy axis is most likely along the [10] direction of the film — an easy axis along [11] is possible, but implies an anomalously small anisotropy. The remanent electron spin polarization depends strongly on the magnetic state, and scattering energy and geometry, illustrating the feasibility of using spin-polarized LEED to study the interdependence of magnetic and electronic structure in this system.