Magnetoresistance relaxation steps originating from dynamic spin-orbital interactions in Ca3Ru2O7

The in-plane magnetoresistance and magnetostriction of Ca3Ru2O7 single crystals were investigated under pulsed magnetic field. Field-induced resistance steps and structural change were observed for specific field directions and far below the metal-to-insulator transition temperature T-MI = 48 K, which were not observed under static magnetic field. Especially, the resistance steps were only observed in the field-descending branch, indicating the relaxation properties, and no magnetization steps were observed. These results unveil the existence of instantaneous interactions among different degrees of freedom in Ca3Ru2O7, which are observable under pulsed magnetic field thanks to its fast field sweep rate. Based on the orbital states of Ca3Ru2O7 and the Kugel-Khomskii model, we propose that the resistance steps and the structural change are related to a dynamic spin-orbital interaction, and this interaction can be strongly suppressed by the magnetocrystalline anisotropy.