Electrical transport properties of thin epitaxially grown iron films

Abstract

We have determined the components of the magnetoresistance tensor through the fifth order in the magnetization direction cosines for four epitaxially grown iron films with thicknesses between 200 and 60 Å at 298, 77, and 4.2 K. We have also determined their magnetic anisotropy parameters, from ferromagnetic resonance, at room temperature. These phenomenological parameters provide an excellent description of the magnetic field dependence of the planar magnetoresistivity for electric current directed along the [100], [011], and [√2 1 1] directions. The magnetization curves of iron films epitaxially grown on GaAs(110) show a first-order transition in the magnetization direction as a function of applied magnetic field. In addition to the single spin flops previously reported in such films, we have observed double spin flops in some of the films. The direction and magnitude of the applied field necessary to produce these consecutive magnetization reorientations have been calculated from the anisotropy parameters, and found to be in excellent agreement with experiment. We speculate that these transitions are caused by the formation and propagation of 90° domain walls. The low residual-resistivity ratios, the large spontaneous Hall coefficients, the likely appearance of conduction-electron localization, and the high resistivities of these iron films constitute evidence for the existence of a large defect density in Fe/GaAs(110).