EPR and optical studies of VO2+ doped diglycine calcium chloride tetrahydrate single crystals

EPR studies of VO2+ doped diglycine calcium chloride tetrahydrate (DGCCT) single crystals are done at room temperature. The results indicate that the paramagnetic impurity takes up a substitutional site in the lattice. The spin Hamiltonian parameters are evaluated using the data of angular variation of EPR spectra in three mutually perpendicular planes and the values are: gx = 1.9976 ± 0.0002, gy = 1.9631 ± 0.0002, gz = 1.9336 ± 0.0002, Ax = (59 ± 2) x 10-4 cm-1, Ay = (81 ± 2) x 10-4 cm-1 and Az = (185 ± 2) x 10-4 cm-1 for Site I and gx = 1.9969 ± 0.0002, gy = 1.9689 ± 0.0002, gz = 1.9306 ± 0.0002, Ax = (49 ± 2) x 10-4 cm-1, Ay = (83 ± 2) x 10-4 cm-1 and Az = (175 ± 2) x 10-4 cm-1 for Site II. The optical absorption study is also done at room temperature. The analysis of the spectrum indicates that the first three bands correspond to d-d transitions and the last band is probably charge transfer band. The band positions were calculated using the energy expressions and compared with the observed band positions to confirm the transitions. The best fit values of the crystal field (Dq) and tetragonal (Ds and Dt) parameters were evaluated from the observed band positions. From optical and EPR data, the bonding parameters are evaluated and the nature of bonding in the crystal is discussed.