Spin-state controlled electronic and magnetic structures of Sr$_{2-x}$La$_{x}$CoO$_{4}$

Sr$_{2-x}$La$_{x}$CoO$_{4}$ is an interesting group of materials, and they display abundant electronic and magnetic properties. In this work, we studied those properties, using electron-correlation corrected density functional calculations. We find that besides a charge-state variation induced by La doping, a multiple spin-state transition takes place and determines (1) a metal-insulator transition and a ferromagnetic insulating phase for $x$=0.5 [1], (2) a paramagnetic Mott insulating phase with a mixed high-spin and low-spin state for $x$=1, instead of a ferromagnetic half-metallic solution with a homogeneous intermediate-spin state [2], and (3) a charge-ordered highly insulating phase with an active spin-blockade mechanism for $x$=1.5 [3]. [1] H. Wu, Phys. Rev. B 86, 075120 (2012). [2] H. Wu, Phys. Rev. B 81, 115127 (2010). [3] H. Wu and T. Burnus, Phys. Rev. B 80, 081105(R) (2009).