Electronic Properties and Dynamic Susceptibility of MnTe Systems

Abstract

Properties of MnTe, CdMnTe systems and especially (Cd)MnTe/CdTe quantum wells have been investigated by using various experimental techniques. Theoretical investigations concerning the band structure calculations were performed mainly for hypothetical MnTe crystals with zinc blende structure as well as for mixed CdMnTe bulk systems (e.g. [1, 2]). Problems of electronic structure and magnetic properties of ultrathin films are undertaken in the paper. Films consisting of 10 MnTe layers with free surfaces of (110) and (100) types are comsidered: Calculations are performed within the framework of the tight-binding approach. Atomic orbitals of d and s symmetry are taken as basis functions for Mn ions, whereas p states are chosen for Te ions. p-d hybridization which plays the crucial role in MnTe systems [2] is strictly taken into account. The Slater-Koster parameterization is used. H oppings between the nearest and the next-nearest neighbours are taken into account. Values of parameters are adjusted in such a way that the main features of the electronic structure characteristic of bulk materials are reproduced in our calculations for bulk MnTe. The splitting of d-bands is assumed to be 7 eV in consistency with experimental data [3]. Calculations are performed for MnTe films with hypothetical ferromagnetic (F) and antiferromagnetic (AFB) order. In the last case the moments are ordered ferromagnetically in planes, but couplings between neighbouring layers are antiferromagnetic. Electronic band structure, local density of states and local magnetic moments are calculated for systems under investigations. Partial densities of states for cations and anions are also found. The obtained results are depicted in Fig. 1. The density of states for the central plane resembles well the one characteristic of