EFFECTS OF APPLIED STRESS ON THE ELECTRON-PARAMAGNETIC RESONANCE-SPECTRA OF NI3+ IN AL2O3

The effects of applied uniaxial stress on the electron paramagnetic resonance (EPR) spectra of Ni3+ in Al2O3 at 9 GHz and at temperatures of 1.2K and 4.2K have been studied. The absorption shapes of the EPR spectra changed from that characteristic of random internal strains to that corresponding to a rather well-defined strain as the stress was increased. The effective Hamiltonian derived in a preceding paper (see ibid., vol.12, p.2133, 1979) for the ground vibronic doublet state was used to fit the experimental data. The parameters so obtained are in good agreement with the fit to the unstressed spectra obtained in the preceding paper. The absence of significant shifts in the lines for large applied stresses implies that the lowest excited vibronic singlet is at least 20 cm-1 above the ground state.