Inelastic Light Scattering Spectroscopy of Magnons and Phonons in Nickel Oxide: Effects of Temperature

TL;DR

This study investigates how magnon and phonon frequencies in NiO change with temperature using inelastic light scattering, revealing persistent antiferromagnetic order above the Neel temperature and offering insights for spintronic applications.

Contribution

It provides a detailed analysis of temperature-dependent magnon and phonon spectra in NiO, including the evolution from zone center to boundary, and introduces laser tuning as a method to distinguish spectral features.

Findings

Magnon and phonon frequencies vary with temperature.

Antiferromagnetic order persists above T_N=523 K.

Laser intensity tuning helps distinguish magnons from phonons.

Abstract

We report results of an investigation of the temperature dependence of the magnon and phonon frequencies in NiO. A combination of Brillouin - Mandelstam and Raman spectroscopies allowed us to elucidate the evolution of the phonon and magnon spectral signatures from the Brillouin zone center (GHz range) to the second-order peaks from the zone boundary (THz range). The temperature-dependent behavior of the magnon and phonon bands in the NiO spectrum indicates the presence of antiferromagnetic (AF) order fluctuation or a persistent AF state at temperatures above the Neel temperature (T=523 K). Tuning the intensity of the excitation laser provides a method for disentangling the features of magnons from acoustic phonons without the application of a magnetic field. Our results are useful for interpretation of the inelastic-light scattering spectrum of NiO, and add to the knowledge of its magnon properties important for THz spintronic devices.