STUDIES OF THE NI3+-AL2O3 SYSTEM BY THERMAL-CONDUCTIVITY MEASUREMENTS

A detailed investigation of the phonon-spin interaction in the system Ni3+:Al2O3 has been carried out by low-temperature thermal conductivity measurements on single crystals (0.05 to 100K). Using the theoretical model of Abou-Ghantous et al. (1974) to describe the vibronic energy levels, a complete quantitative analysis of the data has been achieved with two resonant phonon scatterings at 0.47 cm-1 and 55 cm-1, taking into account the residual strains which play a major role in the low-frequency resonance. From the measurements with applied uniaxial stress the ion-lattice coupling constant has been determined as V Eb=60000+or-9000 cm-1. It has been also possible to estimate the magnitude of the E-type random strains ( approximately=10 -5) and the concentration of the Ni3+ ions in the crystals (0.2 to 5 ppm weight).