Rethinking Physics: Scientists Discover a “Giant” New Twist on a 140-Year-Old Effect

Their results pave the way for developing advanced electronic devices that rely on nonmagnetic materials.

For the first time, researchers in Japan have detected a giant anomalous Hall effect (AHE) in a material that is not magnetic. The breakthrough was made using high-quality thin films of Cd₃As₂, a Dirac semimetal, subjected to an in-plane magnetic field.

By carefully tuning the electronic band structure of the material, the team was able to separate the AHE signal and determine that its source lies in orbital magnetization rather than electron spin, overturning long-standing assumptions in condensed matter physics.

Background on the Hall effect

In 1879, physicist Edwin Hall discovered that an electrical current passing through a conductor placed in a magnetic field generates a voltage across the material. This phenomenon, later named the Hall effect, quickly drew scientific attention and became central to both theoretical and applied physics. Not long afterward, researchers noticed a related effect in magnetic materials, which they called the anomalous Hall effect (AHE).

Unlike the standard Hall effect, the anomalous version has remained far more difficult to explain. For decades, scientists debated its true origin, and some theories suggested that it might even appear in nonmagnetic materials. Until now, however, no experimental evidence had ever confirmed this prediction.

In a recent study, a research team led by Associate Professor Masaki Uchida from Institute of Science Tokyo, Japan, reported the first observation of the AHE in a nonmagnetic material. This breakthrough was published in the journal Physical Review Letters on September 2, 2025.

Role of Dirac semimetals

To make this discovery, the researchers worked with Dirac semimetals. These materials contain special features in their electronic band structure known as Dirac points, where electrons act as though they have no mass. When an external magnetic field is applied, the symmetry of the system breaks, and these Dirac points transform into Weyl points, producing more intricate and directional electron behavior. By carefully adjusting the band structure in this way, the team was able to suppress the ordinary Hall effect and isolate the anomalous Hall effect (AHE) on its own.

“Our study is the first to experimentally confirm that AHE can be quantitatively detected in nonmagnetic materials using in-plane magnetic fields,” notes Uchida.

Using molecular beam epitaxy, the team produced high-quality Cd₃As₂ thin films, a Dirac semimetal with the necessary symmetries. They applied an in-plane magnetic field to these films and measured the Hall conductivity of the material. Based on the changes in this conductivity in response to variations in the applied magnetic field, the researchers could infer the magnitude of the induced AHE. Surprisingly, the team managed to induce a giant AHE with this setup. Detailed analysis of the experimental results suggested that this effect originated from orbital magnetization—that is, magnetization due to the orbital motion of electrons rather than their spin.

Implications for future devices

Taken together, these findings provide valuable insights into a well-studied yet not fully understood physical phenomenon. “The approach used in our study is widely applicable beyond Dirac semimetals, challenging long-standing assumptions about Hall effects. Future research could lead to the development of next-generation devices,” notes Uchida.

Notably, understanding the AHE in more detail opens up pathways to explore electron properties based on orbital magnetization. “We expect these results to catalyze both basic research into the underlying physics and applied research into devices that leverage the AHE,” says Uchida. “Hall sensors and other devices that exploit AHE in nonmagnetic materials could become more efficient and operate under broader conditions than current technologies.”

Reference: “Anomalous Hall Effect in the Dirac Semimetal Cd3As2 Probed by In-Plane Magnetic Field” by Shinichi Nishihaya, Hiroaki Ishizuka, Yuki Deguchi, Ayano Nakamura, Tadashi Yoneda, Hsiang Lee, Markus Kriener and Masaki Uchida, 2 September 2025, Physical Review Letters.
DOI: 10.1103/5d7l-mr7k

Funding: Japan Science and Technology Agency, Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology, Toyota Physical and Chemical Research Institute, Murata Science Foundation, Institute of Science Tokyo, Iketani Science and Technology Foundation

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