147 years after the Hall effect was discovered, scientists show it works in-plane

For 147 years, the Hall effect came with a familiar diagram: electricity moves through a material, a magnetic field pushes the charges sideways, and a voltage appears across the material. Carnegie Mellon researchers have now demonstrated a version that works in a direction long thought impossible.

The team showed that a magnetic field lying within the plane of a material can produce a measurable Hall response. The result, published in Nature Materials, challenges a long-standing assumption in condensed-matter physics and could eventually lead to simpler magnetic sensors that detect fields along multiple directions.

Edwin Hall discovered the effect in 1879. In the conventional arrangement, the magnetic field sits perpendicular to a material carrying an electric current. The resulting voltage can reveal information about the material, including the type and concentration of its charge carriers and how easily they move. Hall sensors now appear in products ranging from cars and keyboards to industrial electronics.

Researchers from Carnegie Mellon’s Lab for Investigating Quantum Materials, Interfaces and Devices began with the two-dimensional quantum material tantalum iridium telluride, or TaIrTe₄. They reduced it to a few atomic layers and placed it beside the magnetic material chromium germanium telluride, or CGT. The close contact allowed the magnetic layer to influence TaIrTe₄, which is normally nonmagnetic.

The resulting atomically thin device produced the familiar Hall signal and a second signal linked to magnetization within the material’s plane. Scientists had predicted this in-plane anomalous Hall effect, but finding a material with the necessary symmetry had made experimental confirmation difficult. A single device that detects fields on multiple axes could eventually reduce the need for separate sensors.