Structural, electronic, and magneto-optical properties of YVO₃

Optical and magneto-optical properties of YVO₃ single crystal were studied in the far-infrared, visible, and ultraviolet regions. Two structural phase transitions at 75 K and 200 K were observed and established to be of first and second order, respectively. The lattice has an orthorhombic Pbnm symmetry both above 200 K as well as below 75 K and is found to be either dimerized monoclinic Pb11 or triclinic P1⁻ in between. We identify YVO₃ as a Mott-Hubbard insulator with an optical gap of 1.6 eV. The visible spectrum shows three d-band excitations at 1.8, 2.4, and 3.3 eV, followed by charge-transfer transitions at about 4 eV. The observed structure is in good agreement with LSDA+U band structure calculations. By using ligand field considerations, we assigned these bands to the transitions to the ⁴A_2g, ²_Eg+²T_1g, and ²T_2g states. The strong temperature dependence of these bands is in agreement with the formation of orbital order. Despite the small net magnetic moment of 0.01_μB per vanadium, a Kerr effect of the order of 0.01° was observed for all three d bands in the magnetically ordered phase (TNéel = K). A surprisingly strong enhancement of the Kerr effect was found below 75 K, reaching a maximum of 0.1°. This effect is ascribed to the nonvanishing net orbital magnetic moment. © 2004 The American Physical Society.