The elevated Curie temperature and half-metallicity in the ferromagnetic semiconductor La$_{x}$Eu$_{1-x}$O

TL;DR

This study demonstrates that La doping in EuO thin films increases the Curie temperature and induces half-metallicity, supported by experimental and theoretical analyses showing magnetic ordering and electronic structure modifications.

Contribution

It provides new insights into enhancing EuO's magnetic and electronic properties through La doping, revealing elevated Curie temperatures and half-metallicity at specific doping levels.

Findings

La doping raises the Curie temperature in EuO films.

La doping induces half-metallicity at doping levels up to 3.2%.

Magnetic ordering is homogeneous and not due to bound magnetic polarons.

Abstract

Here we study the effect of La doping in EuO thin films using SQUID magnetometry, muon spin rotation ($\mu$SR), polarized neutron reflectivity (PNR), and density functional theory (DFT). The $\mu$SR data shows that the La$_{0.15}$Eu$_{0.85}$O is homogeneously magnetically ordered up to its elevated $T_{\rm C}$. It is concluded that bound magnetic polaron behavior does not explain the increase in $T_{\rm C}$ and an RKKY-like interaction is consistent with the $\mu$SR 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 La$_{x}$Eu$_{1-x}$O for increasing lanthanum doping. This reduction of the magnetic moment is explained by the reduction of the number of Eu-4$f$ 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 %.