Spin dynamics of the triplet Cr4+ in the vicinity of energy level anti-crossing

EPR spectra of the triplet Cr4+ in Y2SiO5 were investigated. Rhombic symmet ry of zero-field splitting leads to three electron spin terms T-X, T-Y, and T-Z in the absence of the external magnetic field. We have observed the ma gnetically induced anti-crossing of the terms. In the vicinity of energy le vel anti-crossing the linewidths and positions of the resonance lines depen d on temperature, which is explained by the dynamic Jahn-Teller effect. The temperature dependence of spin relaxation rates is described by the direct spin-lattice relaxation process limited to electron-phonon interactions, w here the phonon frequencies are close to the applied microwave frequency. ( C) 2000 Published by Elsevier Science B.V. All rights reserved.