J.W. Tucker

Magnetization curves of a spin-one Bethe lattice

Abstract An exact calculation of the spontaneous magnetization of a spin-one Ising model with the inclusion of biquadratic exchange and single ion anisotropy on the Bethe lattice is presented. The magnetization curves exhibit some unusual features as the relative strength of the single ion anisotropy is varied.

Nuclear magnetic resonance line-shape and spin correlations in RbMnF3

Abstract The 19 F nuclear magnetic resonance linewidth in RbMnF 3 is expressed in terms of the k -dependent zero frequency limit of the spin relaxation-shape function. A simple choice for this function gives a linewidth in good agreement with experiment.

The memory function approach to the relaxation shape function for the spin 12, X-Y model

Abstract The relaxation shape function obtained by making a Gaussian assumption at the second step in a continued fraction expansion is compared with the exact result and that based on the three-pole approximation of Lovesey and Meserve.

The frequency dependence of phonon scattering by paramagnetic ions

Abstract It is shown that a simplified form of the spin-phonon Hamiltanian can lead to the wrong frequency dependence of the intrinsic linewidth of coupled spin-phonon modes. The importance of this in the interpretation of thermal conductivity experiments is stressed.

Temperature dependence of nuclear magnetic resonance linewidths in RbMnF3

Abstract The temperature dependence of the 55 Mn NMR linewidth in RbMnF 3 is calculated above TN using a representation for the relaxation-shape function based on the method of moments. A room temperature linewidth of 0.90 MHz is obtained in good accord with experiment.

Spin Hamiltonian parameters for 5d ions with a 4A2 ground state in a site of cubic symmetry

Abstract An analytic expression is derived for the Bleaney-Koster-Statz spin hamiltonian parameter, u, of a 4A2 ground state ion in a cubic field that is applicable to 5d ions where the crystal field is the dominant interaction.

The splitting of the 4A2 ground state of Re4+ ions in (NH4)2PtCl6 by trigonal distortions

Abstract Recent EPR measurements on Re4+ ions in (NH4)2PtCl6 by Bufaical and Harris have indicated the presence of non-octahedral centres. An estimation of the degree of distortion of the ReCl6 complex required to account for these results is made.

A general dispersion relation for spin-phonon excitations in paramagnets

Abstract The advantage of using standard basis operators in evaluating the semi-invariants occurring in the diagrammatic theory of spin-phonon modes is discussed. The dispersion relation of the coupled-mode excitations is derived for paramagnetic ions of arbitrary spin having a general static spin hamiltonian.

Orbit-lattice interaction hamiltonian for iron-group ions in tetrahedral co-ordination

Abstract The orbit-lattice hamiltonian for tetrahedrally co-ordinated iron-group ions is presented in terms of operator equivalents in a form that exhibits clearly the symmetry of each component. Rotation modes are included and an error in the current literature corrected.

Concentration dependence of the spin diffusion constant for a diluted Heisenberg magnet

Abstract The concentration dependence of the diffusion constant for a dilute isotropic Heisenberg magnet in the high temperature limit is examined in the cases of simple cubic, body-centered cubic and face-centered cubic lattices with nearest-neighbour exchange.