Influence of epitaxial strain on the ferromagnetic semiconductor EuO: First-principles calculations

From first-principles calculations we investigate the electronic structure and the magnetic properties of EuO under hydrostatic stress and the appropriate biaxial stress for epitaxial films. There is a complex interdependence of the O 2p and Eu 4f and 5d bands on the magnetism in EuO, and decreasing lattice parameters is an ideal method to increase the Curie temperature T(c). Compared to hydrostatic pressure, the out-of-plane compensation that is available to epitaxial films diminishes this increase in Tc, although the Tc increase is nonetheless significant due to the small value of Poisson's ratio for EuO. We find the semiconducting gap closes at a 6% in-plane lattice compression for epitaxy, at which point a significant conceptual change must occur in the active exchange mechanisms.