Eur. Phys. J. B (2015) 88: 82
https://doi.org/10.1140/epjb/e2015-50883-1

Regular Article

Electronic structures of the ferrimagnetic double-perovskites Sr₂XReO₆ (X = Cr, Mn, Fe, Ni) with the modified Becke-Johnson potential

Department of Physics, School of Sciences, China University of Mining and Technology, Xuzhou 221116, P.R. China

^a e-mail: guosd@cumt.edu.cn

Received: 27 December 2014
Received in final form: 28 January 2015
Published online: 1 April 2015

Abstract

We investigate the electronic structures and magnetic properties of the ferrimagnetic double-perovskites Sr₂XReO₆ (X = Cr, Mn, Fe, Ni) by using Tran and Blaha’s modified Becke and Johnson exchange potential. The calculated results show that Sr₂XReO₆ (X = Cr, Fe) are half-metals, and Sr₂XReO₆ (X = Mn, Ni) are insulators, which is in accordance with the experimental results. By using the ionic picture, we explain the trend in the density of states and total magnetic moment with X changing from Cr to Ni. We find that the insulating property is associated with X^{2 +}, while the metallic character is associated with X^{3 +}. The Re t_2g splitting in the minority channel leads to insulativity of Sr₂XReO₆ (X = Mn, Ni), and the Re t_2g splitting of Sr₂MnReO₆ is caused by lattice distortion, while Sr₂NiReO₆’s splitting is due to the heavier atomic mass of Ni. When spin-orbit coupling is included, the spin polarization of Sr₂XReO₆ (X = Cr, Fe) drifts off 100%, and the related gaps of Sr₂XReO₆ (X = Mn, Ni) become narrow. The spin-orbit coupling results in a significant increase in the total magnetic moment due to an unquenched Re orbital moment. Our calculated energy band structures show that Sr₂MnReO₆ is a spin gapless semiconductor, which can realize fully polarized spin-down electrons and spin-up holes.