Electronic structures of the ferrimagnetic double-perovskites Sr<Subscript>2</Subscript>XReO<Subscript>6</Subscript> (X=Cr, Mn, Fe, Ni) with the modified Becke-Johnson potential

We investigate the electronic structures and magnetic properties of the ferrimagnetic double-perovskites Sr<Subscript>2</Subscript>XReO<Subscript>6</Subscript> (X=Cr, Mn, Fe, Ni) by using Tran and Blaha’s modified Becke and Johnson exchange potential. The calculated results show that Sr<Subscript>2</Subscript>XReO<Subscript>6</Subscript> (X=Cr, Fe) are half-metals, and Sr<Subscript>2</Subscript>XReO<Subscript>6</Subscript> (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<Superscript>2 +</Superscript>, while the metallic character is associated with X<Superscript>3 +</Superscript>. The Re t <Subscript>2g </Subscript> splitting in the minority channel leads to insulativity of Sr<Subscript>2</Subscript>XReO<Subscript>6</Subscript> (X=Mn, Ni), and the Re t <Subscript>2g </Subscript> splitting of Sr<Subscript>2</Subscript>MnReO<Subscript>6</Subscript> is caused by lattice distortion, while Sr<Subscript>2</Subscript>NiReO<Subscript>6</Subscript>’s splitting is due to the heavier atomic mass of Ni. When spin-orbit coupling is included, the spin polarization of Sr<Subscript>2</Subscript>XReO<Subscript>6</Subscript> (X=Cr, Fe) drifts off 100%, and the related gaps of Sr<Subscript>2</Subscript>XReO<Subscript>6</Subscript> (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 Sr<Subscript>2</Subscript>MnReO<Subscript>6</Subscript> is a spin gapless semiconductor, which can realize fully polarized spin-down electrons and spin-up holes. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2015