EPR, optical absorption and superposition model studies of Cr3+

Electron paramagnetic resonance (EPR) study of Cr3+ doped cesium tetrabromozincate (CTBZ) single crystal is done at room temperature. The hyperfine structure for Cr53 isotope is also obtained. Two magnetically inequivalent sites for Cr3+ are observed. The spin Hamiltonian parameters are evaluated as: D = 234×10-4cm-1, E = 69×10-4cm-1, g = 2.0104, A = 80×10-4 cm-1 for site I and D = 235×10-4 cm-1, E = 70×10-4cm-1, g = 2.0061, A = 82×10-4cm-1 for site II, respectively. The optical absorption spectra are recorded at room temperature. The energy values of different orbital levels are determined. The values of various parameters obtained are: B = 602 cm-1, C = 2504 cm-1, Dq = 1870 cm-1, h = 1.63 and k = 0.21, where B and C are Racah parameters, Dq is crystal field parameter, and h and k are nephelauxetic parameters, respectively. Theoretical zero-field splitting (ZFS) parameters for Cr3+ at two sites in CTBZ are evaluated using superposition model and microscopic spin Hamiltonian theory. The theoretical ZFS parameters are in good agreement with the experimental values

Electron Paramagnetic Resonance of Mn2+-Doped Cadmium Formate Dihydrate Single Crystals

An electron paramagnetic resonance (EPR) study on Mn2+ doped Cadmium formate dihydrate single crystals is carried out. The EPR spectrum at room temperature exhibits only one out of five fine structural transitions which split into six hyperfine lines in all directions. The spectrum is simulated using the EasySpin program and evaluated spin Hamiltonian parameters. The simulated EPR spectrum is in good agreement with the experiment. By comparing direction cosines of spectroscopic splitting factor g and the direction cosines of different bonds determined by the crystal structure data it is found that Mn2+ enters the lattice substitutionally and only one Mn2+ site is identified. The obtained g and the hyperfine interaction constant A achieved are g = 2.006 ± 0.002, A = (98 ± 2) × 10−4 cm−1 and the second-order axial zero-field splitting parameter D = (60 ± 2) × 10−4 cm−1

ESR and optical study of Cu2+-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II)

ESR studies were conducted on Cu2+-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II). Two Cu2+ lattice sites, Cu2+(I) and Cu2+(II), were identified. These sites exhibit two sets of four hyperfine lines in all directions. The g factor and hyperfine splitting were calculated from ESR absorption spectra: gx = 2.0201 ± 0.002, gy = 2.0900 ± 0.002, gz = 2.1634 ± 0.002, Ax = (30 ± 2) × 10−4 cm−1, Ay = (40 ± 2) × 10−4 cm−1 and Az = (154 ± 2) × 10−4 cm−1. It was found that Cu2+ enters the lattice substitutionally. The ground-state wavefunction of the Cu2+ ion in this lattice was determined from the spin Hamiltonian constants obtained from the ESR studies. With the help of an optical absorption study, the nature of the bonding in the complex is also discussed

Crystalline Field Effect on bonding Parameters of VO2+ Ion

The interpretation of g factor of the VO2+ ion doped in defferent single crystals is made using the Stevens model where the symmetry of the crystalline field is tetragonal. The bonding parameters K|| and K┴, choosing the different parametric angle β, are determined. The value of K┴ should be less than 0.048 in order to have a better fit to the experimental g values

Zero field splitting parameter of Mn2+ doped guanidine zinc sulphate crystal -a theoretical study

A theoretical investigation of crystal field parameters (CFP) and zero-field splitting (ZFS) parameter D of Mn2+ doped guanidine zinc sulphate (GZS) crystals at room temperature (RT) is done with the help of superposition model and the perturbation theory. The ZFS parameter D determined here is in good agreement with the experimental value reported earlier. The conclusion of experimental study that Mn2+ substitutes for Zn2+ in GZS is supported by our theoretical investigation. The values of D without and with local distortion are 11174.3×10-4 cm-1 and 702.4 ×10-4 cm-1, respectively, while the experimental value is 702.0×10-4 cm-1

EPR Studies of Mn 2+ -Doped Diammonium Hexaaqua Magnesium(II) Sulfate

Electron paramagnetic resonance (EPR) studies of Mn 2+ impurity in single crystals of diammonium hexaaqua magnesium(II) sulfate have been carried out at 9.3 GHz (X-band) at room temperature. The EPR spectra exhibit a group of five fine structure transitions. The spin-Hamiltonian parameters were determined. Mn 2+ enters the lattice interstitially. The EPR spectrum of a powder sample supports the data obtained by single crystal studies

Local structure investigation of Cr3+ doped KTP single crystals

Using superposition model (SPM), the crystal field (CF) parameters and zero field splitting (ZFS) parameters of Cr3+ doped KTP single crystals are determined The possible sites for Cr3+ ions in KTP with distortion are taken up for calculation. Considering local distortion the theoretical ZFS parameters are in good agreement with the experimental values. The optical energy values for Cr3+ in KTP are calculated with the help of CF parameters and CFA program. The results show that Cr3+ ions substitute at Ti4+ (2) sites in KTP single crystals

EPR and optical absorption studies on VO2+ ions in l-asparagine monohydrate single crystals

X-Band electron paramagnetic resonance (EPR) studies of VO2+ ions in l-asparagine monohydrate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of two magnetically inequivalent VO2+ sites. Both the vanadyl complexes are found to take up interstitial position. The angular variation of the EPR spectra in three planes ab, bc and ca are used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are, site I: gx = 1.9633, gy = 2.0274, gz = 1.9797, Ax = 88, Ay = 61, Az = 161 × 10−4 cm−1; site II: gx = 1.9627, gy = 1.9880, gz = 1.9425, Ax = 90, Ay = 66, Az = 167 × 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 values. By correlating EPR and optical data different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed

EPR and optical absorption study of Cr3+-doped tetramethyl ammonium cadmium chloride single crystals

EPR study of Cr3+-doped tetramethyl cadmium chloride (TMCC) single crystals is carried out at room temperature. The crystal field and spin-Hamiltonian parameters are evaluated from the resonance line positions of different lines observed in the EPR spectra. The g and D parameter values are found to be g = 1.9741 +/- 0.0002 and D = 553 + 2 x 10(-4) cm(-1), respectively. EPR data indicate that the site symmetry of Cr3+ ion in the crystal is distorted octahedron. Cr3+ ions enter the lattice substitutionally replacing Cd2+ sites and bind to the neighboring extra Cd vacancies necessary for charge compensation. The optical absorption spectra are measured in 195-925 nm wavelength range at room temperature. From optical study the energy values of different orbital levels are estimated. Further, the bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and Q, crystal field parameter (Dq) and nephelauxetic parameters (h and k) are obtained to be B = 722, C = 2845, Dq = 2043 cm(-1), h = 1.015 and k = 0.21