Spin-Wave Spectrum in `Single-Domain' Magnetic Ground State of Triangular Lattice Antiferromagnet CuFeO2

TL;DR

This study uses neutron scattering to investigate spin-wave excitations in a single-domain state of CuFeO2, revealing new dispersion features that highlight the role of lattice effects in its magnetic properties.

Contribution

The paper demonstrates the creation of a nearly single-domain state in CuFeO2 using uniaxial pressure and identifies two spin-wave branches, emphasizing the significance of lattice effects in spin-wave behavior.

Findings

Single-domain state achieved with 10 MPa uniaxial pressure.

Identification of two distinct spin-wave branches.

Discrepancy with previous theoretical models suggests lattice effects are crucial.

Abstract

By means of neutron scattering measurements, we have investigated spin-wave excitation in a collinear four-sublattice (4SL) magnetic ground state of a triangular lattice antiferromagnet CuFeO2, which has been of recent interest as a strongly frustrated magnet, a spin-lattice coupled system and a multiferroic. To avoid mixing of spin-wave spectrum from magnetic domains having three different orientations reflecting trigonal symmetry of the crystal structure, we have applied uniaxial pressure on [1-10] direction of a single crystal CuFeO2. By elastic neutron scattering measurements, we have found that only 10 MPa of the uniaxial pressure results in almost 'single domain' state in the 4SL phase. We have thus performed inelastic neutron scattering measurements using the single domain sample, and have identified two distinct spin- wave branches. The dispersion relation of the upper spin-wave branch cannot be explained by the previous theoretical model [R. S. Fishman: J. Appl. Phys. 103 (2008) 07B109]. This implies the importance of the lattice degree of freedom in the spin-wave excitation in this system, because the previous calculation neglected the effect of the spin-driven lattice distortion in the 4SL phase. We have also discussed relationship between the present results and the recently discovered "electromagnon" excitation.