INVESTIGATION OF THE NATURE OF THE JAHN-TELLER EFFECT FOR NI3+ IN AL2O3 BY ELECTRON-PARAMAGNETIC RESONANCE

Analysis of the electron paramagnetic resonance spectra of Ni3+ in Al2O3 proves conclusively that the Jahn-Teller effect for Ni3+ is dynamic. The Ni3+ ion occupies the trigonal Al3+ sites in Al2O3. Thus the effective Hamiltonian used to describe the spectra resulting from the dynamic Jahn-Teller effect of a vibronic doublet is extended to C3 symmetry using symmetry arguments. This Hamiltonian satisfactorily accounts for the unusual line shapes but the Zeeman interaction is adequately explained by only those terms allowed in Oh symmetry. As the temperature is raised above 1.2K, the highly anisotropic spectrum is averaged by vibronic relaxation yielding a nearly isotropic spectrum.