Enhanced magnetism in Ru-doped hybrid improper perovskite Ca3Mn2O7 via experimental and first-principles study

The quasi-2D Ruddlesden-Popper layered perovskites with single-phase multiferroicity have attracted much attention in recent magnetoelectric memory applications. We have systematically investigated the optical and magnetic properties of Ru-doped hybrid improper perovskite Ca3Mn2O7 both experimentally and using first-principles calculations. The Ca3RuxMn2-xO7 (x = 0, 0.02, 0.06, 0.10) powders were successfully synthesized using the sol-gel method. Ru doping enhanced the ferromagnetism of Ca3Mn2O7. The quasi-2D antiferromagnetic (AFM) fluctuation effect was observed in Ca3Mn2O7 and in certain doped samples. We also found that the optical bandgaps of the doped samples were reduced after doping, agreeing with the results of the first-principles calculations. Infrared absorption spectra indicated the distortion of the Mn-O bonds was possibly due to the Jahn-Teller effect. To analyze the electronic structures and to understand the detailed atomic contributions of magnetic moments, the Crystal Orbital Hamilton Population (COHP) and Integrated COHP of the (Mn,Ru)O-6 octahedra were also calculated. The Ru-doped materials with the coexistence of ferromagnetic and AFM orderings are expected to be excellent candidates for magnetoelectric devices.