ESR spectrum and the theory of zero field splitting for the exchange coupledCu2Cl62minus;dimers in phgr;4AsCuCl3

摘要

Electron paramagnetic resonance has been observed in phgr;4AsCuCl3at room temperature. The spectrum is characteristic of a spin one system. Spin Hamiltonian parameters aregxequals; 2.08,gyequals; 2.11,gzequals; 2.32,Dequals; minus;0.111 cmminus;1, andEequals; 0.009 cmminus;1. The principal axes of thegandDtensor are coincident. The rhombic spin Hamiltonian is a reflection of the distorted tetrahedral environment of the Cu2plus;ions. An expression for the angular dependence of theDtensor components with arbitrary field rotation is developed. The usual method of obtaining the principal axes is discussed. The results from magnetic data compare favorably with the predictions based on structural analysis. The spin Hamiltonian can be rationalized on the basis of a chloride bridged binuclear species. Low temperature spectra show profound increase in intensity but little or no change in line positions. The Cu2plus;ions are pairwise coupled to give a triplet ground state and a singlet excited state at 36 cmminus;1.