Ordering phenomena of spin trimers accompanied by a large geometrical Hall effect

Abstract

Noncoplanar spin trimers are the basic units that define nonzero scalar spin chirality. They are the key ingredients to achieve the chirality-induced geometrical Hall effect. Here, through neutron diffraction, the authors reveal the emergence of noncoplanar Dy${}^{3+}$ spin-trimer units in metallic Dy${}_{3}$Ru${}_{4}$Al${}_{12}$. With a magnetic field, they can control the local spin chirality of the spin trimers as well as its ferroic/antiferroic order. In phases with nonzero total scalar spin chirality, a large geometrical Hall effect is observed. The study reveals that systems composed of tunable spin trimers can be a fertile field for the exploration of a large emergent electromagnetic response, arising from real-space topological magnetic order.