「Specifics of spin excitations in centrosymmetric helimagnets」
Dmytro S. Inosov 氏

Oct 11, 2024

日本物理学会北海道支部講演会

講演題目：　Specifics of spin excitations in centrosymmetric helimagnets
講　師　：　Prof.Dr.rer.nat Dmytro S.Inosov
　　　　　　TU Dresden
日　時　：　2024年10月11日（金）　13：30-
場　所　：　北海道大学理学部 2-221室
要　旨　：
Noncollinear long-range ordered magnetic structures that break chiral symmetry can arise either as a result of Dzyaloshinskii-Moriya interactions in lattices with broken inversion symmetry or as a result of bond frustration in structurally centrosymmetric crystals. While in the former case the spin chirality is uniquely chosen by the lattice symmetry, in the latter case the chiral symmetry is broken spontaneously, so that both right- and left-handed magnetic domains can coexist. Using inelastic neutron scattering, we have studied spin waves in a number of centrosymmetric helimagnets with different magnetic ground states. The cubic spinel ZnCr2Se4 is described by frustrated interactions and represents a perfect model system for studying the Heisenberg model on the perfect pyrochlore lattice. Here, an emergent energy scale of the pseudo-Goldstone magnon gap leads to highly nontrivial thermodynamic and thermal transport properties and to the appearance of a field-induced spiral spin liquid state. The iron perovskite compounds SrFeO3 and Sr3Fe2O7, on the other hand, avoid the simple spin-spiral state and form multiple-q orders of various types, whose spin-wave spectrum is still a challenge for theoretical calculations. At elevated temperatures, all the mentioned compounds exhibit an intense quasielastic spin-fluctuation spectrum in neutron spectroscopy, which coexists with the sharp collective spin-wave excitations and could be a universal feature of the centrosymmetric helimagnets in general. It is possible that its origin is connected with the dynamics of domain walls that separate helimagnetic domains of opposite chirality.
世話人　井原 慶彦
(yihara@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究院物理学部門