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

Abstract

The wavefuntion of conduction electrons moving in the background of a non-coplanar spin structure can gain a quantal phase -Berry phase -as if the electrons were moving in a strong fictitious magnetic field. Such an emergent magnetic field effect is approximately proportional to the solid angle subtended by the spin moments on three neighbouring spin sites, termed the scalar spin chirality. The entire spin chirality of the crystal, unless macroscopically canceled, causes the geometrical Hall effect of real-space Berry-phase origin, whereas the intrinsic anomalous Hall effect (AHE) in a conventional metallic ferromagnet is of the momentum-space Berry-phase origin induced by relativistic spin-orbit coupling (SOC). Here, we report the ordering phenomena of the spin-trimer scalar spin chirality and the consequent large geometrical Hall effect in the breathing kagomé lattice compound Dy3Ru4Al12, where the Dy 3+ moments form non-coplanar spin trimers with local spin chirality. Using neutron diffraction, we show that the local spin chirality of the spin trimers as well as its ferroic/antiferroic orders can be switched by an external magnetic field, accompanying large changes in the geometrical Hall effect. Our finding reveals that systems composed of tunable spin trimers can be a fertile field to explore large emergent electromagnetic responses arising from real-space topological magnetic orders. arXiv:1908.07728v1 [cond-mat.str-el]

Large Hall and Nernst responses from thermally induced spin chirality in a spin-trimer ferromagnet

“…Although the overall crystal structure is centrosymmetric, the inversion center relating two trimers lies between the layers, which thus opens a window for nonzero intratrimer DMI. Previously, the presence of spin-chiral features was reported in Dyand Gd-based isostructural analogs of Nd 3 Ru 4 Al 12 ; static ordering with SSC was found in Dy 3 Ru 4 Al 12 (25), and the emergence of a…”

Anomalous Hall effect in weak-itinerant ferrimagnet FeCr$_2$Te$_4$

“…It is proposed that the FIM in FeCr 2 Te 4 is itinerant ferromagnetism among antiferromagnetically coupled Cr-Fe-Cr trimers [28]. In a noncomplanar spin trimer structures the topologically nontrivial Berry phase is induced by spin chirality rather than spin-orbit effect, resulting in chirality-induced intrinsic AHE [45][46][47][48]. Our result excludes such scenario in Cr-Fe-Cr trimers in FeCr 2 Te 4 [28].…”

Hierarchical excitations from correlated spin tetrahedra on the breathing pyrochlore lattice

“…The corresponding exclusive structure factor S zz can be calculated as: units integrated in the energy range of [2,6] meV for the Ei = 50 meV spectra (a) and [15,25] meV for the Ei = 100 meV spectra. Error bars representing the standard deviations are smaller than the marker size.…”

“…Since a hierarchy in the coupling strengths naturally separates modes of different characteristic energies, magnetic systems composed of alternating bonds offer an incomparable opportunity to achieve novel spin corre-lations that are manifested through effective models [6][7][8][9][10][11]. Clusters with a relatively rigid spin alignment could emerge over the stronger bonds and behave as single entities below a cut-off energy.…”