arXiv subjects

Satoru Ohgata

Publications and source records attributed to Satoru Ohgata.

2 recordsLinked to original sources

arXiv2025

Large Anomalous Hall Effect in Topologically Trivial Double-$Q$ Magnets

Multi-$Q$ magnets consist of superposed spin density waves with distinct magnetic modulation vectors, enabling a wide range of magnetic orders depending on their combination. Among them, topologically nontrivial spin textures, such as a magnetic skyrmion, has been extensively studied owing to the emergence of topological Hall effects induced by real-space scalar spin chirality. Contrary to this expectation, we theoretically investigate another route to enhancing the Hall response under a topologically \textit{trivial} double-$Q$ spin textures. Despite the cancellation of the scalar spin chirality, the double-$Q$ magnetism exhibits a pronounced Hall response with a nonmonotonic dependence on the uniform magnetization, which is in stark contrast to a ferromagnetic state and a single-$Q$ spiral state. Analyzing the multi-orbital Kondo lattice model, we show that orbital hybridization induced by the double-$Q$ superstructure enhances the Berry curvature in $\mathbf{k}$-space, leading to a large anomalous Hall effect. This mechanism accounts for the observed giant anomalous Hall effect in GdRu$_2$Si$_2$ and GdRu$_2$Ge$_2$, thereby highlighting topologically trivial double-$Q$ spin textures as promising spintronic materials.

cond-mat.str-el↗

arXiv2024

Intrinsic anomalous Hall effect under anisotropic magnetic dipole versus conventional magnetic dipole

We theoretically investigate the intrinsic anomalous Hall effect in two magnetically ordered systems: One is the ferromagnetic dipole system, and the other is the anisotropic magnetic dipole system, the latter of which has been proposed as a microscopic indicator of the anomalous Hall effect in antiferromagnets with the negligibly small magnetization. We show their similarity and difference in the anomalous Hall effect by analyzing the fundamental tight-binding model on a two-dimensional square lattice. We find that the magnitudes of the anomalous Hall effect in the two systems are similar to each other, while the magnetization in the anisotropic magnetic dipole system is much smaller than that in the ferromagnetic dipole system; this indicates that the microscopic mechanisms are different from each other. We show that such a difference appears in the momentum-resolved Berry curvature resulting from the different types of magnetic order parameters. We also show that the anomalous Hall effect in the anisotropic magnetic dipole system is enhanced when the magnitude of the spin-orbit coupling is smaller than that of the magnetic mean field. Our results provide a possibility of the giant anomalous Hall effect in collinear and coplanar antiferromagnetic systems with the anisotropic magnetic dipole.

cond-mat.mes-hall↗