Ultrasonic investigation of a phase transition in ZnSe:Ni

Abstract

Ultrasonic experiments on ZnSe and ZnSe:Ni crystals with impurity concentrations of 5.5×10 19 cm -3 have revealed precursor phenomena at temperatures much higher than the temperature of the structural transition (T c =14.5K). It is found that the elastic constant C 44 softens while C 11 and C 12 become stiffer as T c is approached from above; the strains associated with the order parameter are transverse deformations of the ε 4 type. A brief symmetry analysis of the possibilities of formation of a tetragonal phase is given. The Jahn-Teller effect and displacement of the charge density on the chemical bonds are discussed as probable causes of the low-temperature phase transition. © 2004 American Institute of Physics.