Raman scattering due to a one-magnon excitation process in $\mathrm{Mn}{\mathrm{V}}_2{\mathrm{O}}_4$

Abstract

Unconventional peak structure in the Raman spectra due to magnon excitation at low temperature is observed in spinel magnet $\mathrm{Mn}{\mathrm{V}}_2{\mathrm{O}}_4$, where a noncollinear spin state is realized by geometrical frustration. We propose a new mechanism to induce such a Raman scattering process due to a one-magnon excitation of the noncollinear spin state. Novel features of the scattering such as selection rules and peak position observed experimentally in $\mathrm{Mn}{\mathrm{V}}_2{\mathrm{O}}_4$ can be explained quite naturally by considering the present one-magnon process. We also discuss that such one-magnon process may exist in various materials with noncollinear spin structures.

5 pages, 4 figures