EFFECT OF MAGNETIC-FIELD ON THE SOUND-VELOCITY OF A DILUTE KRAMERS-ION GLASS AT LOW-TEMPERATURE

Recent results on the effect of magnetic field on the sound velocity V in aluminosilicate glasses doped with dysprosium are analyzed on the basis of a minimal model for the ground state of Dy3+ (Kramers ion wit h J = 15/2) described by a wave function phi(+/-) = phi(+/-Jm) + eta p hi(+/-1/2). The first term represents a state with a large J projectio n on the local crystal field axis and the random parameter eta([eta] = 0, [eta(2)] much less than 1) introduces a small admixture of the sta te phi(+/-1/2) into the ground state. The relative variation of V due to the resonance interaction of sound waves with this state split by H is determined as a function of H and T. It possesses a universal asym ptotic behavior. Our results are in reasonable agreement with the expe riment. A possible structure of the crystal fields that can induce thi s state is discussed (C) 1997 American Institute of Physics.