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

摘要

ABSTRACT: A comparative study of the crystal and electronicnstructure and magnetism of divalent europium perovskite oxidesnEuMO3 (M = Ti, Zr, and Hf) has been performed on the basis ofnboth experimental and theoretical approaches playing complementarynroles. The compounds were synthesized via solid-statenreactions. EuZrO3 and EuHfO3 have an orthorhombic structurenwith a space group Pbnm at room temperature contrary tonEuTiO3, which is cubic at room temperature. The optical bandngaps of EuZrO3 and EuHfO3 are found to be about 2.4 and 2.7neV, respectively, much larger than that of EuTiO3 (0.8 eV). Onnthe other hand, the present compounds exhibit similar magneticnproperties characterized by paramagnetic-antiferromagnetic transitionsnat around 5 K, spin flop at moderate magnetic fields lowernthan 1 T, and the antiferromagnetic nearest-neighbor andnferromagnetic next-nearest-neighbor exchange interactions. First-principles calculations based on a hybrid Hartree−Fockndensity functional approach yield lattice constants, band gaps, and magnetic interactions in good agreement with those obtainednexperimentally. The band gap excitations are assigned to electronic transitions from the Eu 4f to M nd states for EuMO3 (M = Ti,nZr, and Hf and n = 3, 4, and 5, respectively).