Structural, electronic and magnetic properties of a ferromagnetic metal: Nb-doped EuTiO3

Abstract

Experimentally, ferromagnetic and metallic behaviors of Nb-doped EuTiO3 were reported. Until now, first-principle computational study has not been carried out to investigate the origin of the FM interactions in doped EuTiO3. Here, structural, electronic and magnetic properties of Nb-doped EuTiO3 are investigated using hybrid density functional theory method. The calculated results show that the entire series of EuTi1−xNbxO3 (0 ≤ x ≤ 1) stabilize in a cubic perovskite structure. EuTi1−xNbxO3 is an antiferromagnetic insulator at x = 0 and a ferromagnetic metal at 0.125 ≤ x ≤ 1, which agrees well with available experiments. Nb doping induces itinerant electrons into the conduction band bottom at 0.125 ≤ x, and the Fermi level moves upward. As a result, the Ruderman-Kittel-Kasuya-Yosida (RKKY)-type interaction, between Eu2+ spins by the itinerant Ti 3d and Nb 4d electrons, can be responsible for ferromagnetism in EuTi1−xNbxO3. The present study provides a theoretical understanding of origin of ferromagnetism in EuTi1−xNbxO3 and is helpful to understand FM interactions of other doped EuTiO3. For EuTi0.5Nb0.5O3, arranging the Ti and Nb atoms into a 1 × 1 EuTiO3/EuNbO3 superlattice along the [0 0 1] direction results in interesting FM metallic properties, which are not present in the parent compound EuTiO3 but similar to those of EuNbO3.