Elevated Curie temperature and half-metallicity in the ferromagnetic semiconductor LaxEu1-xO

Abstract

Here we study the effect of La-doping in EuO thin films using superconducting quantum interference device magnetometry, muon spin rotation (μSR), polarized neutron reflectivity (PNR), and density functional theory (DFT). The μSR data shows that the La0.15 Eu0.85O is homogeneously magnetically ordered up to its elevated TC. It is concluded that bound magnetic polaron behavior does not explain the increase in TC and an Ruderman-Kittel-Kasuya-Yosida-like (RKKY-like) interaction is consistent with the μSR data. The estimation of the magnetic moment by DFT simulations concurs with the results obtained by PNR, showing a reduction of the magnetic moment per LaxEu1-xO for increasing lanthanum doping. This reduction of the magnetic moment is explained by the reduction of the number of Eu-4f electrons present in all the magnetic interactions in EuO films. Finally, we show that an upwards shift of the Fermi energy with La or Gd doping gives rise to half-metallicity for doping levels as high as 3.2%.