HIGH-PRESSURE INDUCED STRUCTURAL PHASE TRANSITION AND ELASTIC PROPERTIES OF DILUTED MAGNETIC SEMICONDUCTORS Zn1-xMnxSe

Abstract

An effective interionic interaction potential is developed to study the pressure-induced phase transitions from zinc blende (B3) to rock salt (B1) structure in diluted magnetic semiconductors Zn 1-x Mn x Se (x=0.08 and 0.15). As a first step, the elastic constants, including the long-range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction up to second-neighbor ions within the Hafemeister and Flygare approach, are derived. Assuming that both the ions are polarizable, the Slater–Kirkwood variational method is employed to estimate the vdW coefficients. The estimated values of the phase transition pressure (Pt) increase with Mn concentration. The vast volume discontinuity in the pressure volume phase diagram identifies the structural phase transition from zinc blende to rock salt structure. The variation of second-order elastic constants with pressure resembles that observed in some binary semiconductors. It is noticed that the vdW interaction is effective in obtaining the thermodynamical parameters such as Debye temperature, Gruneisen parameter, and thermal expansion coefficient. However, the inconsistency in the value of pressure derivative of the theoretical and experimental value of C44 is attributed to the fact that we have derived the expressions by assuming that the overlap repulsion is significant only up to nearest neighbors, as well as neglecting thermal effects.