Spin-phonon coupling in BaFe12O19 M-type hexaferrite

TL;DR

This study investigates the temperature-dependent Raman spectra of BaFe12O19 to detect spin-phonon coupling at its ferrimagnetic transition, revealing an anomaly in phonon behavior indicative of such coupling.

Contribution

It provides the first experimental evidence of spin-phonon coupling in BaFe12O19 at the ferrimagnetic transition temperature.

Findings

Anomaly observed in phonon position at 720 K.

Spin-phonon coupling varies among different phonons.

Confirmation of spin-phonon coupling in BaFe12O19.

Abstract

The spin-phonon coupling in magnetic materials is due to the modulation of the exchange integral by lattice vibrations. BaFe12O19 M-type hexaferrite, which is the most used magnetic material as permanent magnet, transforms into ferromagnet at high temperatures, but no spin-phonon coupling was previously observed at this transition. In this letter, we investigated the temperature-dependent Raman spectra of polycrystalline BaFe12O19 M-type hexaferrite from room temperature up to 780 K to probe spin-phonon coupling at the ferrimagnetic transition. An anomaly was observed in the position of the phonon attributed to the Fe(4)O6 octahedra, evidencing the presence of a spin-phonon coupling in BaM in the ferrimagnetic transition at 720 K. The results also confirmed the spin-phonon coupling is different for each phonon even when they couple with the same spin configuration.