Distance Dependence of the Mn-Mn Exchange Interaction in IV-VI Semimagnetic Semiconductors

Abstract

In the present paper we calculate the exchange interaction between two manganese ions in IV-VI semiconductors with the rocksalt structure. The method of calculations is based on the fourth order perturbation theory with respect to hybridization between band states and localized d orbitals of Mn ions. This hybridization is described by three Harrison integrals: V p d σ , V p d π , and V s d σ . The band states of IV-VI semiconductor are obtained from the semiempirical tight binding model built from s and p orbitals of cations and anions. The resulting exchange term in the Hamiltonian is of the form - Σ i , j = x y z J i j S 1 i S 2 j , however nondiagonal terms of the exchange integral tenso J i > not = j are very small. The dependence of J i j on the Mn-Mn distance is non-monotonic. We also discuss the influence of the local crystal deformations on the exchange integral.