Possible magnetic ground state of the half doped perovskite compound R 0.5Ce 0.5CoO 3 (R=Ca, Sr)

Abstract

By using the unrestricted Hartree–Fock approximation and the real-space recursion method, we have investigated various magnetic structures in an enlarged double cell of the half doped compound R 0.5Ce 0.5CoO 3 (R=Ca, Sr). These include the low-spin state ( LS : t 2 g 5 e g 1 ) , the intermediate-spin state ( IS : t 2 g 4.5 e g 1.5 ) , and the high-spin state ( HS : t 2 g 4 e g 2 ) as well as all possible combinations among these three states. The densities of states are computed and stabilities of various states are analyzed as functions of the model parameters. For a fixed Hund's coupling j, it is shown that the ground state of R 0.5Ce 0.5CoO 3 (R=Ca, Sr) transforms from the antiferromagnetic high-spin state to the ferromagnetically ordered high-spin low-spin state as the crystal-field splitting Dq increases.