DATE2025.09.17 #Press Releases

Discovery of the In-Plane Anomalous Hall Effect in Ferromagnetic Materials

-Demonstration of Off-Diagonal Coupling Between Orbital and Spin Magnetization-

Summary

A research group led by Associate Professor Masaki Uchida (Department of Physics, School of Science, Science Tokyo) in collaboration with Associate Professor Hiroaki Ishizuka’s group (Department of Physics, School of Science, Science Tokyo) and Professor Ryotaro Arita’s group (Graduate School of Science, The University of Tokyo / Team Director, RIKEN Center for Emergent Matter Science) has successfully observed the anomalous Hall effect in ferromagnetic materials with in-plane magnetization.

The Hall effect, in which the flow of electrons is deflected by a magnetic field, has played an essential role in understanding electron transport phenomena in solids and has been of great importance for both research and applications for over a century. Traditionally, the Hall effect has been understood as arising mainly from out-of-plane magnetic fields or the corresponding out-of-plane spin magnetization perpendicular to the current, and many electronic devices such as Hall sensors have been designed within this framework. However, in this study, by utilizing ultrathin films of strontium ruthenate (SrRuO₃), which possesses Weyl points in its band structure, the researchers realized a state with spontaneous in-plane spin magnetization. They revealed that an anomalous Hall effect emerges with out-of-plane orbital magnetization, even without applying an external magnetic field.

By performing measurements while precisely controlling the zenith and azimuthal angles of the applied magnetic field, the team confirmed that the Hall resistivity varies systematically depending on the direction of spin magnetization. These results demonstrated that the off-diagonal coupling between orbital and spin magnetization is at the heart of this phenomenon. The discovery overturns the conventional understanding of the Hall effect and opens new avenues for exploring and applying electronic properties based on orbital magnetization.

The results of this research were published in Advanced Materials on September 16, 2025 (U.S. Eastern Time).

Figure:(Top) Dependence of anomalous Hall resistivity on in-plane magnetic fields at a specific azimuthal angle. (Bottom) Results of measuring Hall resistivity after sweeping the magnetic field up to 9 T and back to zero, while changing the zenith angle from out-of-plane to in-plane directions.

Links

Science Tokyo, RIKEN, Toyota Physical and Chemical Research Institute, Japan Science and Technology Agency（JST）

Journals

Journal name	Advanced Materials
Title of paper	Spontaneous in-plane anomalous Hall response observed in a ferromagnetic oxide