First principles investigation of half-metallicity and spin gapless semiconductor in CH3NH3CrxPb1-xI3 mixed perovskites

The structural, electronic and magnetic properties of organic-inorganic hybrid mixed perovskites CH3NH3CrxPb1-xI3 (x = 0.25, 0.50, 0.75, 1.00) in cubic, tetragonal and orthorhombic phases have been investigated by first-principles calculation. The results indicate that the tetragonal CH3NH3Cr0.75Pb0.25I3 is a spin gapless semiconductor with Curie temperature of 663 K estimated using mean field approximation. All other CH3NH3CrxPb1-xI3 mixed perovskites are half-metallic ferromagnets together with 100% spin polarization, and their total magnetic moment are 4.00, 8.00, 12.00 and 16.00 mu(B) per unit cell for x = 0.25, 0.50, 0.75 and 1.00, respectively. The effect of < 100 >, < 110 > and < 111 > orientation of organic cation CH3NH3+ on the electronic properties of CH3NH3Cr0.50Pb0.50I3 was investigated. The results show that the CH3NH3+ in different orientations have a slight effect on the lattice constants, the energy gap in minority-spin states, half-metallic gap, local magnetic moment, and Curie temperature.