Spin Reorientation and Large Anomalous Hall Effect in the Metallic Kagome Ferromagnet LaCo₄B

The kagome lattice, a two-dimensional network of corner-sharing triangles, has attracted significant attention in quantum materials research due to its inherent geometric frustration and the resulting exotic magnetic states. Rare-earth-based kagome systems are particularly intriguing as they combine geometrical frustration, strong spin–orbit coupling, and electron correlations arising from 4f–3d interactions. While insulating compounds often exhibit suppressed or fragile magnetic order, metallic rare-earth kagome systems reveal complex couplings between localized rare-earth moments and itinerant electrons, giving rise to large anomalous Hall effects, heavy fermion behavior, and tunable magnetic anisotropy.

Among these, the cobalt-based intermetallics YCo₄B and LaCo₄B provide a model platform to investigate how lattice expansion influences magnetic anisotropy and spin-reorientation behavior within the Co sublattice. We have grown single-crystalline LaCo₄B using isotopically enriched B¹¹ flux and performed detailed structural, magnetic, and transport characterizations. X-ray diffraction confirms a hexagonal P6/mmm structure with lattice parameters a = 5.2012(6) Å , and c = 6.8939(8) Å. Magnetization measurements reveal a ferromagnetic transition at 315 K and a spin-reorientation transition near 250 K, accompanied by a strong magnetic anisotropy with the ab plane as the easy axis.

Furthermore, a large anomalous Hall conductivity (~600 Ω^-1cm^-1 ) is observed, suggesting a substantial Berry-curvature contribution to the charge transport. The magnetoresistance also shows strong anisotropy depending on field orientation, indicating a close interplay between spin configuration and electronic structure. These results establish LaCo₄B as a metallic kagome ferromagnet hosting tunable spin reorientation and significant Berry-curvature–driven transport phenomena.