A theoretical study of the elastic properties of dysprosium antimonide

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Abstract
The author develops an expression for the softening of an elastic constant of dysprosium antimonide. This softening is due to a Jahn-Teller coupling between magnetic ions whose ground manifolds are split into several levels by a crystalline field. This expression is evaluated in the molecular-field approximation and further approximated by considering only quadrupolar interactions. A good fit to the thermal variation of the elastic constant of dysprosium antimonide Ctheta =1/2(C11-C12) is obtained by suitably choosing the background elastic constant, the Jahn-Teller strain coupling gtheta and the biquadratic coupling Itheta . Several physical mechanisms are discussed which give rise to the fitted values of the parameters and to the structural and magnetic phase transition at 9.5K. It is concluded that the phase transition is driven by approximately equal amounts of strain coupling gtheta and exchange interactions.