Scientists Discover New “Hall Effect” That Could Revolutionize Electronics

Scientists discovered a new Hall effect driven by spin currents in noncollinear antiferromagnets, offering a path to more efficient and resilient spintronic devices.

A research team led by Colorado State University graduate student Luke Wernert and Associate Professor Hua Chen has identified a previously unknown type of Hall effect that could lead to more energy-efficient electronic devices.

Their study, published in Physical Review Letters, was conducted in collaboration with graduate student Bastián Pradenas and Professor Oleg Tchernyshyov of Johns Hopkins University. The researchers uncovered evidence of a new property, dubbed the “Hall mass,” in a class of complex magnetic materials known as noncollinear antiferromagnets.

The traditional Hall effect, discovered by Edwin Hall at Johns Hopkins in 1879, describes how an electric current is deflected sideways when subjected to an external magnetic field, generating a measurable voltage. This effect plays a crucial role in technologies such as vehicle speed sensors and smartphone motion detectors.

But in the CSU team’s work, electrons’ spin (a tiny, intrinsic form of angular momentum) takes center stage instead of electric charge. Noncollinear antiferromagnets, unlike more familiar magnets where spins line up parallel or antiparallel, have spins oriented in different directions but still sum to zero net magnetization. This unique spin texture enables a fresh take on the Hall effect, where spin currents can flow at right angles rather than just electric charges.

The Role of Spin Currents and Hall Mass

“Imagine pushing a spin current in one direction and getting a second spin current going sideways,” Wernert explains. “That’s the hallmark of a Hall effect.” The reason this new effect—governed by the “Hall mass”—appears only in noncollinear antiferromagnets is because they have three degrees of freedom describing spin orientations.

This extra complexity leads to three branches of spin waves (collective vibrations of the spins), two of which naturally flow sideways in response to a driving force.

Experimentally, researchers can measure this Hall mass either by injecting spin waves from a conventional ferromagnet into a noncollinear antiferromagnet and detecting spin accumulation along the edges, or by using scattering techniques (like neutron or x-ray) to track the low-energy spin-wave spectrum.

Implications for Spintronics and Future Technology

Because spin currents produce far less heat than electrical currents, harnessing them could revolutionize modern electronics. This prospect underlies the rapidly growing field of “spintronics,” which strives to build devices—such as magnetic-based storage (Magnetoresistive Random-Access Memory, MRAM)—that are more energy efficient and resistant to data corruption by external magnetic fields.

In conventional magnetic materials, a stray magnetic field can sometimes wipe out stored information; by contrast, noncollinear antiferromagnets are much less susceptible to such interference, making them potentially safer for data storage and handling. Altogether, the discovery of this new Hall effect and its associated Hall mass opens an exciting direction in condensed matter physics and could guide the development of next-generation technology powered by spin.

Reference: “Hall Mass and Transverse Noether Spin Currents in Noncollinear Antiferromagnets” by Luke Wernert, Bastián Pradenas, Oleg Tchernyshyov and Hua Chen, 3 January 2025, Physical Review Letters.
DOI: 10.1103/PhysRevLett.134.016706

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