Electronic band structure and properties of the solid solution Eu$_{1-x}$Fe$_x$O

The electronic band structure of the solid solution Eu$_{1-x}$Fe$_x$O ($x$ = 0.0625, 0.125) involved in the composition of the spintronic composite EuO: Fe has been calculated using the full-potential linearized augmented- plane-wave (FLAPW) method. The calculations have been performed with the correction of the exchange–correlation potential in the framework of the generalized gradient approximation (GGA + $U$). It has been shown that iron and europium cations have the oxidation state close to 2+. In this case, the iron cations are in the high-spin state with the magnetic moment close to 4 $\mu_{\mathrm{B}}$, which explains the significant increase in the Curie temperature of the composite upon doping of EuO with iron. It has been demonstrated that there is a small transfer of the electron density from Eu$^{2+}$ cations to Fe$^{2+}$ cations. It has been argued that the main factor providing a high concentration of Eu$^{3+}$ cations in the composite is, probably, the presence of Eu$_2$O$_3$ nanoclusters in the structure.