First-principles investigation of magnetic coupling mechanism in A-site-ordered perovskite CaFe _3Ti _4O _(12)

摘要

We have investigated the electronic and magnetic properties of A-site-ordered perovskite CaFe _3Ti _4O _(12) using first-principles calculations. Our calculated results indicate that CaFe _3Ti _4O _(12) is mechanically stable and it is an antiferromagnetic insulator. Similar to its isostructural perovskite CaCu _3Ti _4O _(12), the primary magnetic coupling mechanism in CaFe _3Ti _4O _(12) is ascribed to the Fe-O-Ti-O-Fe superexchange interaction. From this fact we can clearly see that the empty 3d orbitals play an important role to realize the superexchange interaction. Moreover, comparing CaFe _3Ti _4O _(12) and CaCu _3Ti _4O _(12) in some details, we find that Fe (Cu)-O bond distance is one of the important parameters to determine the antiferromagnetic strength within this superexchange interaction.