Crystal and Electronic Structure and Magnetic Properties of Divalent Europium Perovskite Oxides EuMO3 (M = Ti, Zr, and Hf): Experimental and First-Principles Approaches

A comparative study of the crystal and electronic structure and magnetism of divalent europium perovskite oxides EuMO3 (M = Ti, Zr, and Hf) has been performed on the basis of both experimental and theoretical approaches playing complementary roles. The compounds were synthesized via solid-state. reactions. EuZrO3 and EuHfO3 have an orthorhombic structure with a space group Pbnm at room temperature contrary to EuTiO3, which is cubic at room temperature. The optical band gaps of EuZrO3 and EuHfO3 are found to be about 2.4 and 2.7 eV, respectively, much larger than that of EuTiO3 (0.8 eV). On the other hand, the present compounds exhibit similar magnetic properties characterized by paramagnetic-antiferromagnetic transitions at around 5 K, spin flop at moderate magnetic fields lower than 1 T, and the antiferromagnetic nearest-neighbor and ferromagnetic next-nearest-neighbor exchange interactions. First-principles calculations based on a hybrid Hartree-Fock density functional approach yield lattice constants, band gaps, and magnetic interactions in good agreement with those obtained experimentally. The band gap excitations are assigned to electronic transitions from the Eu 4f to M nd states for EuMO3 (M = Ti, Zr, and Hf and n = 3, 4, and 5, respectively).