Paramagnetic Resonance Spectrum of Gadolinium in LaAlO3

Abstract

The resonance spectrum of ${\mathrm{Gd}}^{3+}$ in LaAl${\mathrm{O}}_3$ was investigated as a function of the temperature. It was found that the trigonal parameter $b_2^{}{}_{}{}^0$ changes smoothly from 67×${10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$ at 689°K to 491×${10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$ at 20°K. The transition to cubic phase is found by extrapolation to be at 720±15°K. The spin Hamiltonian appropriate to the trigonal phase is given by $H=g\beta \mathbf{H}·\mathbf{S}+B_2^{}{}_{}{}^{0}O_2^{}{}_{}{}^0+B_4^{}{}_{}{}^{0}O_4^{}{}_{}{}^0+B_6^{}{}_{}{}^{0}O_6^{}{}_{}{}^0+B_4^{}{}_{}{}^{3}O_4^{}{}_{}{}^3+B_6^{}{}_{}{}^{3}O_6^{}{}_{}{}^3+B_6^{}{}_{}{}^{6}O_6^{}{}_{}{}^6$. The evaluation of the magnitude of the various parameters $B_m^{}{}_{}{}^n$ is presented.