Rewriting Textbooks: Physicists Discover Anomalous Hall Effect Where It Shouldn’t Exist

New research unveils the first experimental evidence of the anomalous Hall effect arising in a collinear antiferromagnet exhibiting non-Fermi liquid behavior.

A team of international researchers, led by Mayukh Kumar Ray, Mingxuan Fu, and Satoru Nakatsuji of the University of Tokyo, in collaboration with Collin Broholm from Johns Hopkins University, has observed the anomalous Hall effect in a collinear antiferromagnetic, a phenomenon previously thought to be exclusive to ferromagnets. Even more remarkably, this effect arises from a non-Fermi liquid state, where electrons behave in ways that deviate from conventional theoretical models.

This discovery, published in Nature Communications, challenges established textbook explanations of the anomalous Hall effect and expands the range of antiferromagnetic materials that could be harnessed for future information technologies.

In simple terms, electrons possess an intrinsic property called spin, which can be thought of as pointing “up” or “down.” In ferromagnetic materials, these spins align in the same direction, producing a net magnetization. This alignment can give rise to the anomalous Hall effect, where an electric voltage appears perpendicular to an applied current even in the absence of an external magnetic field.

Antiferromagnets, on the other hand, have spins aligned in opposite directions, canceling out overall magnetization. Conventional wisdom suggests that such materials should not exhibit the anomalous Hall effect.

A Search for Magnetization-Free Hall Effects

“There have been previous reports on the anomalous Hall effect appearing in a certain class of collinear antiferromagnets,” says Nakatsuji, the principal investigator. “However, the observed signals were extremely weak. Identifying a truly magnetization-free anomalous Hall effect was of broad scientific and technological interest.”

This endeavor required coordination across various groups. Fu and her colleagues were responsible for the experimental setup to measure the effect. They used a family of materials called transition metal dichalcogenide (TMD) as two-dimensional (2D) building blocks. By inserting magnetic ions between the atomic layers, the researchers could control the movements and interactions of electrons.

The modified structure, now in 3D, had the potential to exhibit new behaviors that could not have been possible in only 2D. At last, the researchers could make measurements of the anomalous Hall effect across a wide range of temperatures and magnetic fields. In addition, Broholm’s group’s provided microscopic evidence confirming the collinear antiferromagnetic structure of the material. The results were then combined with the theoretical analysis and calculations done by Ryotaro Arita’s group at UTokyo.

“One of the main challenges in our research project has been constructing a coherent scientific narrative from our observations,” says Fu, a co-lead of the paper. “Each step required careful interpretation, especially due to the structural disorder commonly found in transition metal dichalcogenide (TMD) systems.”

A Paradigm Shift in Magnetism Research

The resulting measurement is the first strong experimental evidence for the anomalous Hall effect observed in collinear antiferromagnets. As the anomalous Hall effect is commonly believed to go hand in hand with magnetization, the detection suggests that something far beyond the standard understanding is at play. Researchers suspect the phenomenon is rooted in the unique structure of the material’s electron bands, causing a large “virtual magnetic field” and boosting the anomalous Hall effect in the absence of magnetization. Nakatsuji explains the next steps.

“We are seeking experimental confirmation for this hypothesis and actively pursuing a range of follow-up studies using complementary techniques, including Raman spectroscopy, to uncover the underlying mechanisms.”

Reference: “Zero-field Hall effect emerging from a non-Fermi liquid in a collinear antiferromagnet V1/3NbS2” by Mayukh Kumar Ray, Mingxuan Fu, Youzhe Chen, Taishi Chen, Takuya Nomoto, Shiro Sakai, Motoharu Kitatani, Motoaki Hirayama, Shusaku Imajo, Takahiro Tomita, Akito Sakai, Daisuke Nishio-Hamane, Gregory T. McCandless, Michi-To Suzuki, Zhijun Xu, Yang Zhao, Tom Fennell, Yoshimitsu Kohama, Julia Y. Chan, Ryotaro Arita, Collin Broholm and Satoru Nakatsuji, 18 April 2025, Nature Communications.
DOI: 10.1038/s41467-025-58476-0

Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.