Multiple-<i>q</i> noncollinear magnetism in an itinerant hexagonal magnet.

Abstract

Multiple-<i>q</i> spin order, i.e., a spin texture characterized by a multiple number of coexisting magnetic modulation vectors <i>q</i>, has recently attracted attention as a source of nontrivial magnetic topology and associated emergent phenomena. One typical example is the triple-<i>q</i> skyrmion lattice state stabilized by Dzyaloshinskii-Moriya interactions in noncentrosymmetric magnets, while the emergence of various multiple-<i>q</i> states of different origins is expected according to the latest theories. Here, we investigated the magnetic structure of the itinerant polar hexagonal magnet Y₃Co₈Sn₄, in which several distinctive mechanisms favoring multiple-<i>q</i> states are allowed to become active. Small-angle neutron-scattering experiments suggest the formation of incommensurate triple-<i>q</i> magnetic order with an in-plane vortex-like spin texture, which can be most consistently explained in terms of the novel four-spin interaction mechanism inherent to itinerant magnets. The present results suggest a new route to realizing exotic multiple-<i>q</i> orders and that itinerant hexagonal magnets, including the <i>R</i> ₃ <i>M</i> ₈Sn₄ family with wide chemical tunability, can be a unique material platform to explore their rich phase diagrams.