U.S. Ghosh

The variation of elastic constants of nickel-iron single crystal alloys from 78.76 TO 300 K

Abstract The temperature dependences of the three independent adiabatic elastic stiffness coefficients c 11 , C 12 and C 44 of four Ni-Fe single crystal alloys with compositions from 50 to 90 wt.% of Ni have been studied by the ultrasonic pulse superposition technique from 78.76 to 300 K. The elastic constants of the alloys exhibit normal temperature dependencies in the range of temperature investigated. A good fit of the experimental data to Lakkads phenomenological model for the temperature dependence of elastic constants was obtained.

Ligand field theory of the magnetic behaviours of tetrahedrally coordinated Cu2+ ion in Cs2CuCl4

The theoretical expression for gs, magnetic susceptibility and anisotropy of Cu2+ ion having tetragonal symmetry in the tetrahedral caesium chlorocuprate (II) have been derived following Pryces Spin Hamiltonian formalism in terms of the ligand field coefficients and also taking into consideration the anisotropic covalency effects. Attempts have been made to fit the experimental data of optical absorption, g-values, magnetic susceptibility and anisotropy with a unique set of values of parameters in the theoretical expressions at all temperatures. The result of such fitting indicates that there must be a change in the anisotropic field with temperature. Further, there is an appreciable anisotropic overlap between the 3d charge cloud of copper and the p charge clouds of chlorines.

Investigations on the orthorhombic g-tensors in Cu(KSeO4)2, 6H2O and Cu(NH4SeO4)2, 6H2O crystals by E.P.R. technique

Electron paramagnetic resonance technique has been applied to find precisely the orientations of the orthorhombic g-tensors and their principal magnitudes in CuK2(SeO4)2, 6H2O and Cu(NH4)2, (SeO4)2, 6H2O crystals. These orientations of the orthorhombic axes can not be obtained from any other magnetic measurement and may serve as a fruitful complement to the determination of structure by X-rays. The present investigation also throws some light on the nature of the ligand field in copper Tutton salts—especially its symmetry, its variation from salt to salt belonging to the isomorphous series and the long range effect arising from outside the primary ligand cluster.

Effect of crystal field on the spin density at the copper nucleus in copper complexes

The role of lower symmetry component of the crystal field in causing a mixing of excited 3dx−1 4s with the ground 3dx configuration and leading to spin density at the nucleus for iron group ions was suggested by Griffith and Orgel. This mechanism has been examined in detail for the two low-symmetry copper complexes, one square planar (D4h symmetry) and the other distorted tetrahedron (D2d symmetry) and the calculation has been performed using the powerful Racah method and tensor operator technique. It is found that for the two types of copper complexes, copper pthalocyanin (square planar, D4h symmetry) and cesium copper chloride (distorted tetrahedron, D2d symmetry) the contribution from this mechanism to the spin density at the nucleus vanishes identically.