Magnetic and transport properties of degenerate ferromagnetic semiconductor EuO

Abstract

By applying the coherent potential approximation (CPA) to simple models, we have studied the temperature $(T)$ dependence of the normalized magnetization $M(T)$, and electrical resistivity $\ensuremath{\rho}(T)$ of highly rare-earth-doped EuO. The present result reveals that in degenerate EuO, the magnetization is described by an electron-doped EuO model; the strong double-dome feature of $M(T)$ of Gd-doped EuO is a consequence of the half-metallicity and low dopant activation. In degenerate EuO, the temperature dependence of the resistivity is well described by Matthiessen's rule as $\ensuremath{\rho}(T)={\ensuremath{\rho}}_{C}+{\ensuremath{\rho}}_{m}(M)$, where ${\ensuremath{\rho}}_{C}$ is the nonmagnetic scattering contribution (independent of $T$) and ${\ensuremath{\rho}}_{m}(M)$ is the magnetic scattering contribution due to the exchange interaction with localized $f$ spins. ${\ensuremath{\rho}}_{C}$ is proportional to $x(1\ensuremath{-}x)/{n}^{\frac{2}{3}}$, while the amplitude of the change in ${\ensuremath{\rho}}_{m}(M)$ is proportional to ${n}^{\ensuremath{-}\frac{2}{3}}$, where $x$ is the doped rare-earth density and $n$ is the electron density. The difference in $M(T)$ and $\ensuremath{\rho}(T)$ between Gd- and La-doped EuO is also discussed.