Experimental and computational investigation of the polar ferrimagnet VOSe2O5

We have re-examined the crystal structure and the physical properties of VOSe2O5 by performing single crystal X-ray and powder neutron diffraction, alternating current (AC) and direct current (DC) magnetization measurements, heat capacity, dielectric properties, and second-harmonic generation (SHG) measurements. From these studies, we observed that the compound undergoes three magnetic transitions near 4, 5.5, and 8 K. In addition, we observed ferrimagnetic behavior as the magnetic ground state, confirmed by the isothermal magnetization measured below 8 K that reveals a saturated magnetic moment of 0.5 μB per formula unit, consistent with density functional calculations of the magnetically ordered ground state. We propose a ferrimagnetic spin arrangement that is consistent with neutron diffraction measurements as well. Frequency dependence in the AC magnetic susceptibility, observed at 5.5 K, is considered as short-range magnetic ordering and may be associated with the competition between nearest neighbor and next nearest neighbor interactions of the V4+ cations. A dielectric anomaly near 240 K and non-centrosymmetric functional properties, notably, second harmonic generation and electric polarization, are also discussed. © 2010 American Chemical Society.