NQR of35Cl in paramagnetic and antiferromagnetic K2IrCl6

Abstract

Measurements of the 35Cl nuclear quadrupole resonance as a function of temperature and magnetic field above the Neel point of K2IrCl6 are interpreted as providing no direct evidence of a proposed phase transition suggested to explain certain infrared measurements. The temperature dependence of the nqr lines is fitted to the simple Bayer theory, although the theory does not appear adequate for a complete description. Below the Neel point the nqr line splits into seven separate lines which can be explained in terms of transferred hyperfine interactions at each of the chlorine nuclei, in part due to the existence of molecular orbitals on the IrCl6 complexes. Deviations from the hyperfine interactions of the molecular orbitals suggest additional transferred hyperfine interactions from neighbouring ions of chlorine, which may be a result of the superexchange between iridium ions in the antiferromagnetic state.