Kagome lattice promotes chiral spin fluctuations

Abstract

Magnetic materials with tilted electron spins often exhibit conducting behavior that cannot be explained from semiclassical theories without invoking fictitious (emergent) electromagnetic fields. Quantum-mechanical models explaining such phenomena are rooted in the concept of a moving quasiparticle's Berry phase, driven by a chiral (left- or right-handed) spin-habit. Dynamical and nearly random spin fluctuations, with a slight bent towards left- or right-handed chirality, represent a promising route to realizing Berry-phase phenomena at elevated temperatures, but little is known about the effect of crystal lattice geometry on the resulting macroscopic observables. Here, we report thermoelectric and electric transport experiments on two metals with large magnetic moments on a triangular and on a slightly distorted kagomé lattice, respectively. We show that the impact of chiral spin fluctuations is strongly enhanced for the kagomé lattice. Both these spiral magnets have similar magnetic phase diagrams including a periodic array of magnetic skyrmions. However, our modelling shows that the geometry of the kagomé lattice, with corner-sharing spin-trimers, helps to avoid cancellation of Berry-phase contributions; spin fluctuations are endowed with a net chiral habit already in the thermally disordered (paramagnetic) state. Hence, our observations for the kagom\,e material contrast with theoretical models treating magnetization as a continuous field, and emphasize the role of lattice geometry on emergent electrodynamic phenomena.

16 pages, 4 figures

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• Anisotropic skyrmion and multi-$q$ spin dynamics in centrosymmetric Gd${}_2$PdSi${}_3$
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• Anomalous Electrical Transport in the Kagome Magnet YbFe${}_6$Ge${}_6$
• From chiral spin liquids to skyrmion fluids and crystals, and their interplay with itinerant electrons
• Frustration and chirality in three-dimensional trillium lattices: Insights and Perspectives
• Metal-insulator transitions in pyrochlore oxides
• Magnetic ground state and perturbations of the distorted kagome Ising metal TmAgGe
• Correlation between Complex Spin Textures and the Magnetocaloric and Hall Effects in Eu(Ga${}_{1-x}$Al${}_x$)${}_4$ ($x$ = 0.9, 1)
• Anomalous Hall effect in the antiferromagnetic Weyl semimetal SmAlSi
• Large unconventional anomalous Hall effect far above room temperature in epitaxial Fe${}_3$Ga${}_4$ films
• Collinear ferromagnetism with reduced moment length in kagome magnet Nd3Ru4Al12
• Classification of mass terms in kagome semimetals