Jahn-Teller parameters of MgO:Cr2+determined using heat pulses

A strong scattering of phonons at level anticrossings in the low-lying states of Cr 2+ in MgO has been observed as a function of magnetic fields. The observed spectra was found to be turning points, with respect to strain, of the magnetic fields at which level anti-crossings occurred. The B//(100) data could be accounted for by a computer diagonalization of the lowest fifteen eigenvalues on the basis of the theory of Fletcher and Stevens (1969) the values 3 Lambda =32+or-6 cm -1 are obtained for the tunnelling splitting and D=2.5+or-0.5 cm -1 for the reduced spin-orbit coupling, with the sign of the warping parameter, B positive.