An interpretation of the g factors for the tetragonally-compressed Cr5+ centers in YVO4 and YPO4 crystals

The g factors g∥ and g⊥ for the tetragonally-compressed (CrO4)3− clusters in YMO4 (M=V, P) crystals are calculated from the high-order perturbation formulas based on the two-mechanism model for the compressed d1 tetrahedra with the ground state |dz2〉. From the calculated values and by considering a small admixture of the first excited state |dx2−y2〉 to the ground state |dz2〉 due to the vibrational motion of ligands (which leads a twinkling compressed tetrahedron to become an elongated one), the observed g∥ and g⊥ for Cr5+ centers in YMO4 crystals are explained reasonably. The difficulty of the large deviations of g∥ from ge (≈2.0023) in the two systems is therefore removed and the above dynamic effect may be the cause which results in the large deviation of g∥ from ge for some (CrO4)3− clusters in crystals.