Temperature and Field Dependence of Ferromagnetic Magnon in Monolayer Honeycomb Spin Lattice

TL;DR

This study explores how temperature and magnetic field influence ferromagnetic magnons in monolayer honeycomb lattices, revealing phase transitions, magnon behavior, and applying the model to CrI₃ with quantitative insights.

Contribution

It introduces an anisotropic XZ-Heisenberg model to analyze magnon dynamics and phase transitions in monolayer honeycomb lattices, including real material application to CrI₃.

Findings

Magnon intensity persists above the spin reorientation temperature.

The zero-momentum magnon gap closes at the critical transverse field.

Estimated magnon velocity near Dirac point is approximately 1.74 km/s.

Abstract

Temperature and field dependence of collective spin excitations or magnon in monolayer honeycomb spin lattices is investigated using an anisotropic exchange XZ-Heisenberg model in an external field. Magnetic phase transition in the presence of the transverse field is the spin reorientation (SR) transition with magnon intensity existing above the SR temperature. The transverse field either decreases or sustains the spin-wave intensity in the temperature region below or above the SR temperature, respectively. The gap of the zero-momentum low-energy magnon branch closes at the SR transverse field, which is the critical quantum phase transition field at zero temperature. The application of the model to a two-dimensional CrI$_3$ explains the existence of the zero-momentum magnon mode above the Curie temperature and shows the suitable values of the exchange parameters compared with the DFT calculations. The estimated magnon velocity near the Dirac point in this material is about 1.74 km/s.