Magnetic and electronic interaction effects at the interfaces ofFe∕V2O3andCo∕V2O3bilayers

Abstract

Thin films of ${\mathrm{V}}_{2}{\mathrm{O}}_{3}(11\overline{2}0)$ can exist in metallic and insulating phases with different magnetic properties, similar as the bulk single crystals. We have used macroscopic magnetometry and x-ray absorption spectroscopy together with magnetic circular dichroism to show that when these films are combined with thin overlayers of bcc Fe and hcp Co, this has a pronounced impact on the electronic and magnetic properties of the interfaces. While the uncovered oxide is metallic at room temperature, both ferromagnets induce an insulating phase near the surface of the oxide, presumably due to hybridization effects at the interface. Remarkably, the electronic interaction across the interface is significantly different for the two systems. This is reflected in a magnetically ``dead'' atomic layer in the Fe films at the interface, a property not observed in the Co films. As a consequence the magnetic anisotropy of the two ferromagnets is dissimilar. In the antiferromagnetic phase of ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$, at $Tl{T}_{N}\ensuremath{\approx}160\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the hysteresis loops of the Co films exhibit a significant exchange bias; the effect is absent for Fe. The faceted surface structure of the ${\mathrm{V}}_{2}{\mathrm{O}}_{3}(11\overline{2}0)$ layers induces a uniaxial magnetic anisotropy with magnetocrystalline and magnetostatic contributions in both ferromagnetic overlayers.