Multiple components of the spin-rotational excitations in hexagonal RMnO3 (R = Lu, Y) single crystalline systems

초록

Spin-rotational excitations in hexagonal RMnO3 (R = rare-earths, Y) are believed to be due to localized rotations of the Mn3+ spins in the triangular lattice through the resonance with the Mn d-d transition of the incident and/or scattered photons in the Raman scattering process. In this study, we confirmed experimentally that the spin-rotational excitations are localized within the undisturbed Mn-ion trimers, by comparing the LuMn1−xFexO3 (magnetic Fe-ion substitution) and YMn1−yAlyO3 (non-magnetic Al-ion substitution) systems. Analyses using the two-dimensional correlation spectroscopy (2D-COS) revealed that the spin-rotational Raman peaks consist of multiple overlapping components rather than being single broad peaks. Variations in the spin–spin integral J and effective S values due to imperfections and substitution would be continuous so that they may lead to a single broad peak. Therefore, existence of the multiple components is an important finding in understanding the nature of the spin-rotational excitations. The new finding suggests the possibilities of multiple states with discrete energy differences ∼meV near the ground state and the spin-rotated state which are transient states excited during the steady-state resonance Raman scattering process in the anti-ferromagnetically ordered state of the hexagonal RMnO3 (R = Lu, Y) systems. © 2026 The Author(s)