Energy-Resolved Ultrafast Spectroscopic Investigation on the Spin-Coupled Electronic States in Multiferroic Hexagonal HoMnO3.

A complete temperature-dependent scheme of the Mn3+ on-site d-d transitions in multiferroic hexagonal HoMnO3 (h-HoMnO3) thin films was unveiled by energy-resolved ultrafast spectroscopy. The results unambiguously revealed that the ultrafast responses of the e1g and e2g states differed significantly in the hexagonal HoMnO3. We demonstrated that the short-range antiferromagnetic and ferroelectric orderings are more relevant to the e2g state, whereas the long-range antiferromagnetic ordering is intimately coupled to both the e2g and e1g states. Moreover, the primary thermalization times of the e2g and e1g states were 0.34 ± 0.08 ps and 0.38 ± 0.08 ps, respectively.