Electron Correlations, Spin-Orbit Coupling, and Antiferromagnetic Anisotropy in Layered Perovskite Iridates Sr2IrO4**Supported by the Key Research Program of Frontier Sciences, Chinese Academy of Sciences under Grant No. QYZDB-SSW-SYS012 and National Natural Science Foundation of China (Project 11747601), and Numerical Calculations were Performed on the HPC Cluster of ITP-CAS

Abstract

The effects of electron correlations and spin-orbit coupling on the magnetic anisotropy in the antiferromagnetically ordered 5d perovskite iridates Sr2IrO4 is investigated theoretically using a microscopic model includes a realistic five-orbital tight-binding Hamiltonian, atomic spin-orbit coupling, and multi-orbital Hubbard interactions. Hartree-Fock approximation is applied to obtain the ground state properties with varying spin-orbit coupling and electron correlations. We demonstrate that the interplay between the atomic intraorbital Coulomb repulsion and the Hundʼs rule coupling leads to a remarkable variability of the resulting magnetic anisotropy at a constant nonzero spin-orbit coupling. At the same time, the preferred direction of the ordered antiferromagnetical moment remains unaltered upon changes in the strength of spin-orbit coupling.