Model analysis of magnetic susceptibility of Sr$_2$IrO$_4$ - 2D $J_{\rm eff}$ = 1/2 Heisenberg system with competing interlayer couplings

TL;DR

This paper analyzes the magnetic susceptibility of Sr$_2$IrO$_4$ using a theoretical model that incorporates Heisenberg antiferromagnetism, Dzyaloshinsky-Moriya interaction, and competing interlayer couplings, explaining experimental observations.

Contribution

It develops a comprehensive theoretical susceptibility model for Sr$_2$IrO$_4$ that includes interlayer couplings and explains the magnetic behavior above the Néel temperature.

Findings

Model accurately describes susceptibility above $T_N$

Identifies competition between interlayer couplings

Explains in-plane canting moments configuration

Abstract

We report the analysis of magnetic susceptibility $\chi$($T$) of Sr$_2$IrO$_4$ single crystal in the paramagnetic phase. We formulate the theoretical susceptibility based on isotropic Heisenberg antiferromagnetism incorporating the Dzyaloshinsky-Moriya interaction exactly, and include the interlayer couplings in a mean-field approximation. $\chi$($T$) above $T_{\rm N}$ was found to be well described by the model, indicating the predominant Heisenberg exchange consistent with the microscopic theory. The analysis points to a competition of nearest and next-nearest neighbor interlayer couplings, which results in the up-up-down-down configuration of the in-plane canting moments identified by the diffraction experiments.