Santwana Shukla

EPR and optical studies of Cu2+ ions doped in magnesium potassium phosphate hexahydrate single crystals

An electron paramagnetic resonance (EPR) study of Cu2+-doped magnesium potassium phosphate is performed at liquid nitrogen temperature (LNT; 77 K). Two magnetically non-equivalent sites for Cu2+ are observed. The spin Hamiltonian parameters are determined with the fitting of spectra to a rhombic symmetry crystalline field. The ground state wavefunction is also determined. The g-anisotropy is evaluated and compared with the experimental value. With the help of an optical study, the nature of the bonding in the complex is discussed.

EPR and Optical Absorption Study of VO2+-Doped Lithium Hydroxylammonium Sulphate

ABSTRACT Single-crystal and powder EPR studies of VO2+-doped lithium hydroxylammonium sulphate (LiNH3OHSO4) were carried out at room temperature. The results indicate the presence of two magnetically inequivalent VO2+ sites. The VO2+ ion takes up a substitutional position in the host lattice. The angular variation of EPR spectra in three mutually perpendicular planes were used to determine the spin Hamiltonian parameters, and the values obtained were the following: For Site 1, gx = 2.0249 ± 0.0002, gy = 1.9698 ± 0.0002, gz = 1.9552 ± 0.0002, Ax = (51 ± 2) × 10−4 cm−1, Ay = (93 ± 2) × 10−4 cm−1, and Az = (165 ± 2) × 10−4 cm−1; and for Site 2, gx = 2.0267 ± 0.0002, gy = 1.9743 ± 0.0002, gz = 1.9213 ± 0.0002, Ax = (40 ± 2) × 10−4 cm−1, Ay = (80 ± 2) × 10−4 cm−1, and Az = (155 ± 2) × 10−4 cm−1. The optical absorption spectrum recorded at room temperature shows four bands. From the optical and EPR data, various molecular coefficients are evaluated, and the nature of bonding in the crystal is discussed.

ESR and optical studies of Cu2+ doped zinc glutamate dihydrate.

The ESR study of the Cu2+ doped zinc glutamate dihydrate is carried out at room temperature. Two magnetically nonequivalent sites for Cu2+ are observed. The spin Hamiltonian parameters are determined with the fitting of spectra to rhombic symmetry crystalline field. The parameters are as follows: Cu2+(I): gx=2.0170±0.0002, gy=2.0768±0.0002, gz=2.2334±0.0002, Ax=(74±2)×10(-4), Ay=(99±2)×10(-4), Az=(134±2)×10(-4) cm(-1)and Cu2+(II): gx=2.0180±0.0002, gy=2.0550±0.0002, gz=2.1633±0.0002, Ax=(100±2)×10(-4), Ay=(100±2)×10(-4), Az=(115±2)×10(-4) cm(-1). The ground state wave function is also determined. The g-anisotropy is evaluated and compared with the experimental value. Using the data of optical absorption study undertaken at room temperature the nature of bonding in the complex is also discussed.

Electron Paramagnetic Resonance and Optical Absorption of VO2+ Doped Bis (glycinato) Mg (II) Monohydrate Single Crystals

We investigate the electron paramagnetic resonance (EPR) of VO2+ ions in bis (glycinato) Mg (II) monohydrate single crystals at room temperature. Detailed EPR. analysis indicates the presence of only one VO2+ site. The vanadyl complexes are found to take up the substitutional position. The angular variation of the EPR spectra in three planes a*b, be and ca* are used to determine principal g and A tensors. The values of spin Hamiltonian parameters are gx = 2.1447×10−4, gy = 1.9974×10−4, gz = 1.9131×10−4, Ax = 49×10−4, Ay = 60×10−4, Az = 82×10−4 cm−1. The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental data. By correlating EBB. and optical data, different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.

Electron paramagnetic resonance and optical absorption study of VO2+-doped sodium zinc sulfate tetrahydrate single crystals

Single-crystal electron paramagnetic resonance (EPR) studies of VO2+ doped in sodium zinc sulfate tetrahydrate (Na2Zn(SO4)2·4H2O) have been carried out at room temperature. The results show the presence of three magnetically inequivalent VO2+ sites with different populations. The VO2+ impurity ions take up substitutional positions in the host lattice replacing Zn2+ ions. The angular variation of EPR spectra in three mutually orthogonal planes, bc, a*c and ba*, are used to determine the spin-Hamiltonian parameters. The optical absorption spectrum of VO2+ ions doped in the crystal lattice is also recorded at room temperature in the wavelength range 325–1100 nm. This is utilized to study the energy level structure of the VO2+ ion. By correlating the EPR and optical data, various molecular orbital coefficients of the VO2+ ion with its ligands are evaluated and the nature of bonding in the crystal is discussed.

C4ν Symmetry Crystal Field and Ground State Wavefunction of the VO2+ Ion

The spin-Hamiltonian parameters obtained from EPR studies of the VO2+ ion in different diamagnetic host lattices are used to estimate the ground state wave functions. These are of dxy type with admixture of the excited states dx2−y2, dyz and dxz. The hyperfine interaction parameter and Fermi contact term for the VO2+ doped crystals are determined using the coefficients of the ground state. The various parameters are correlated to the ligand properties of the complexes.