Microscopic model for the ground state, 1/3 plateau and excitations of $\gamma$-Mn$_3$(PO$_4$)$_2$

TL;DR

This paper develops a magnetic model for $$-Mn$_3$(PO$_4$)$_2$ that explains its ground state, 1/3 magnetization plateau, and excitations by fitting experimental data and including biquadratic coupling and anisotropy.

Contribution

It introduces a comprehensive exchange Hamiltonian incorporating biquadratic coupling and anisotropy to explain experimental magnetic phenomena.

Findings

The model reproduces observed field transitions.

It accounts for multiple phase transitions in susceptibility.

Magnetic spectrum aligns with low-temperature specific heat data.

Abstract

We present a magnetic model for an antiferromagnetic compound $\gamma$-Mn$_3$(PO$_4$)$_2$, which was previously shown to exhibit a 1/3 magnetization plateau due to the trimer-based structure of the lattice of magnetic Mn$^{2+}$ ions with $S=5/2$. An exchange Hamiltonian that yields observed field transitions is obtained from fitting magnetization data. It is shown that both biquadratic coupling and single-ion anisotropy are necessary to be present in the magnetic model to explain multiple phase transitions in the magnetic susceptibility data. The calculated magnetic spectrum is in agreement with the low-temperature specific heat data.