Magnetic reorientation transition in a three orbital model for Ca2RuO4—interplay of spin–orbit coupling, tetragonal distortion, and Coulomb interactions

Abstract

Including the orbital off-diagonal spin and charge condensates in the self consistent determination of magnetic order within a realistic three-orbital model for the 4d4 compound Ca2RuO4, reveals a host of novel features including strong and anisotropic spin–orbit coupling (SOC) renormalization, coupling of strong orbital magnetic moments to orbital fields, and a magnetic reorientation transition. Highlighting the rich interplay between orbital geometry and overlap, SOC, Coulomb interactions, tetragonal distortion, and staggered octahedral tilting and rotation, our investigation yields a planar antiferromagnetic (AFM) order for moderate tetragonal distortion, with easy a–b plane and easy b axis anisotropies, along with small canting of the dominantly yz, xz orbital moments. With decreasing tetragonal distortion, we find a magnetic reorientation transition from the dominantly planar AFM order to a dominantly c axis ferromagnetic order with significant xy orbital moment.