Band engineering of modified rhombohedral Cu4Mn2Te4: ab initio approach

Abstract

ABSTRACT Systematic band structure calculations are reported for the first time on the ‘modified rhombo (R-3 m) structured Cu4Mn2Te4’ compound by adapting the Lotgering model. Wyckoff positions of all the atoms are estimated. There is a good agreement between the present computed lattice parameter values with the already reported. Mechanism of phase transition from Fd-3m structure (3Cu added spinel CuMn2Te4) to R-3m structure (distorted rhombo Cu4Mn2Te4) at room temperature is discussed. Spin-polarised calculations reveal Cu4Mn2Te4 energetically prefers the AFM phase at ambient conditions. Band structures predict the compound to be of metallic nature at its NM and FM phases whereas a band gap opening occurs at its AFM phase. Band gap value is estimated as ∼ 0.2 eV and ∼0.7 eV using GGA and mBJ exchange–correlation schemes, respectively. Origin of band gap opening is discussed. Total spin magnetic moment (µB ) per formula unit of Cu4Mn2Te4 compound is calculated as 9.878 and −5.001, respectively, at FM and AFM phases. Electrical conductivity is enhanced by a factor of 102 from 100 K to 300 K at minority spin states. Maximum optical conductivity occurs at 6500 Ω−1cm−1 which lies in the visible region of the electromagnetic spectrum.