Magnetic Properties of Eu-Doped GaN Grown by Molecular Beam Epitaxy

Magnetic properties of molecular-beam epitaxy grown Eu-doped GaN are studied. At high temperatures, clear hysteresis and clear saturation indicating the existence of a ferromagnetic-like phase are observed in the magnetization versus magnetic curves, while at low temperatures gradually saturating nonlinear field dependence of the magnetization is also observed. The easy-axis for the ferromagnetization is perpendicular to the sample plane. A theoretical model is proposed to account for the experimental results, assuming that a molecular field is acting on Eu ions via the spin-polarized valence-band of GaN. The experimental results are accounted for by assuming the coexistence of Eu 2+ ions and Eu 3+ ions interacting through the Ruderman-Kittel-Kasuya-Yoshida-type interaction.