Driving spin excitations by hydrostatic pressure in BiFeO3

TL;DR

This study combines optical spectroscopy, computational, and theoretical methods to investigate how hydrostatic pressure influences spin excitations and structural phases in multiferroic BiFeO3, revealing pressure-induced changes in magnetic dynamics.

Contribution

It provides a comprehensive analysis of pressure-driven spin excitation evolution in BiFeO3 using combined experimental and theoretical approaches, highlighting the role of structural phases and magnetic anisotropy.

Findings

Multiple spin excitations collapse into two under pressure.

Discontinuous jumps in excitations at structural phase transitions.

Structural phases and magnetic anisotropy control spin excitations.

Abstract

Optical spectroscopy has been combined with computational and theoretical techniques to show how the spin dynamics in the model multiferroic BiFeO3 responds to the application of hydrostatic pressure and its corresponding series of structural phase transitions from R3c to the Pnma phases. As pressure increases, multiple spin excitations associated with non-collinear cycloidal magnetism collapse into two excitations, which show jump discontinuities at some of the ensuing crystal phase transitions. Effective Hamiltonian approach provides information on the electrical polarization and structural changes of the oxygen octahedra through the successive structural phases. The extracted parameters are then used in a Ginzburg-Landau model to reproduce the evolution with pressure of the spin waves excitations observed at low energy and we demonstrate that the structural phases and the magnetic anisotropy drive and control the spin excitations.