One- and two-magnon excitations in antiferromagnet PbFeBO4

TL;DR

This study uses linear spin-wave theory to analyze magnon excitations in PbFeBO4, identifying optical and two-magnon modes, deriving exchange interactions, and revealing minimal magnon-magnon interactions.

Contribution

It provides a detailed theoretical analysis of magnon excitations in PbFeBO4, including exchange constants and interaction effects, based on experimental and ab initio data.

Findings

Identification of optical magnon and two-magnon excitations in Raman spectra

Derivation of exchange coupling constants up to third neighbors

Negligible role of magnon-magnon interactions in two-magnon band shape

Abstract

The linear spin-wave theory study of PbFeBO4 spin dynamics is presented. It is shown that the modes observed in Raman scattering experiments below Neel temperature are optical magnon and two-magnon excitations. Based on the magnon energy, two-magnon band lineshape, and Weiss temperature, the consistent set of the exchange coupling constants up the third neighbor is derived and compared with the results of ab initio calculations. The small deviation of the observed two-magnon band from the one-magnon density of states suggests a surprisingly negligible role of magnon-magnon interactions.