Fluctuation-driven topological Hall effect in room-temperature itinerant helimagnet Fe3Ga4
Priya R. Baral, Victor Ukleev, Ivica Živković, Youngro Lee, Fabio Orlandi, Pascal Manuel, Y. Skourski, L. Keller, A. Stunault, J. Alberto Rodríguez‐Velamazán, R. Cubitt, Arnaud Magrez, J. S. White, I. I. Mazin, O. Zaharko
Abstract
The topological Hall effect (THE) is a hallmark of a non-trivial geometric spin arrangement in a magnetic metal, originating from a finite scalar spin chirality (SSC). The associated Berry phase is often a consequence of non-coplanar magnetic structures identified by multiple k-vectors. For single - k magnetic structures however with zero SSC, the emergence of a finite topological Hall signal presents a conceptual challenge. Here, we report that a fluctuation-driven mechanism involving chiral magnons is responsible for the observed THE in a low-symmetry compound, monoclinic Fe3Ga4. Through neutron scattering experiments, we discovered several nontrivial magnetic phases in this system. In our focus is the helical spiral phase at room temperature, which transforms into a transverse conical state in applied magnetic field, supporting a significant THE signal up to and above room temperature. Our work offers a fresh perspective in the search for novel materials with intertwined topological magnetic and transport properties. The topological Hall effect usually results from a static scalar spin chirality. Here, through a combination of neutron scattering and transport measurements, Baral et al. demonstrate the emergence of a room temperature topological Hall effect due to dynamic scalar spin chirality in a topologically non-trivial phase in Fe3Ga4