EPR studies on local structure of 70V₂O₅-30P₂O₅ glass at 4K

590-593From the obtained spin-Hamiltonian parameters of the axially symmetric lineshape of the glass at 4K it is concluded that the paramagnetic site in the glass is vanadyl ion, VO2+. The vanadium is in distorted octahedral environment of six oxygens forming a O- VO4..O unit. This geometry of C4v symmetry leads to the value of the coefficient of 3dxy orbital β as 0.96 and the Fermi contact term the measure of the vanadium 4sorbital contribution to bonding as 0.75. The crystal field splitting energy, tetragonal distortion energy and spin-orbit coupling constant are found to be 23186, 12056 and 169 cm-1, respectively. From the above values, it is concluded that O- VO4•••O unit has highly 'squeezed' VO4 group with moderate axial compression. The vanadium 3d1 small polaron gets localized on a 51V(I= 7/2)site at 4s due to the 'Anderson localization' and thereby the symmetry of the local structure of the glass is reflected in its EPR lineshape