Magnetic susceptibility of the body-centred orthorhombic La$_2$CuO$_4$ system

TL;DR

This paper models the magnetic susceptibility of La$_2$CuO$_4$'s orthorhombic phase, incorporating spin-orbit and interplanar interactions, and compares theoretical predictions with experimental data.

Contribution

It introduces a comprehensive Hamiltonian model for La$_2$CuO$_4$'s magnetic properties, including spin-orbit effects and interplanar exchange, and simplifies it to a tetragonal model that retains accuracy.

Findings

The model matches experimental susceptibility data.

The tetragonal approximation reproduces magnon spectra.

The Hamiltonian captures key magnetic interactions.

Abstract

A model Hamiltonian representing the Cu spins in La$_2$CuO$_4$ in its low-temperature body-centred orthorhombic phase, that includes both spin-orbit generated Dzyaloshinskii-Moriya interactions and interplanar exchange, is examined within the RPA utilizing a Tyablikov decoupling of various high-order Green's functions. The magnetic susceptibility is evaluated as a function of temperature and the parameters quantifying these interactions, and compared to recently obtained experimental data of Lavrov, Ando and collaborators. An effective Hamiltonian corresponding to a simple tetragonal structure is shown to reproduce both the magnon spectra and the susceptibility of the more complicated body-centred orthorhombic model.