In 1879, American physicist Edwin Hall identified the Hall effect. This phenomenon occurs when an electric current flowing through a conducting material is deflected to one side under the influence of a perpendicular magnetic field, resulting in a measurable voltage. Sensors utilizing this effect have found widespread application. For more than a century, the academic community has held the belief that the Hall effect manifests solely when the magnetic field is perpendicular to the material.

However, a research team from Carnegie Mellon University has challenged this long-held notion. In a paper published in Nature Materials, they reported that by stacking an atomic-layer-thick topological semimetal, TaIrTe₄, with a ferromagnetic insulator, CGT, they observed a Hall response even when the magnetic field was parallel to the material's b-axis. This represents the first-ever observation of an in-plane magnetization-driven anomalous Hall effect in a two-dimensional system.

Through meticulous experiments, the team confirmed that this effect originates from the magnetic layer. They found that the magnitude of the response is intricately linked to crystal symmetry. Moreover, the response can be finely tuned by adjusting the gate voltage. Importantly, they ruled out any interference from the planar Hall effect.

This groundbreaking discovery has the potential to rewrite traditional physical laws. It is expected to simplify applications such as multi-dimensional magnetic field sensing, enabling vector magnetic measurements with a single sensor. This advancement holds promise for various fields, including attitude detection, automotive systems, and medical imaging. However, it's worth noting that the current experiments were conducted at a low temperature of approximately minus 262 degrees Celsius. The research team is actively exploring material combinations that can operate at room temperature. They have also developed a two-band model to qualitatively explain the effect, but more precise theories still warrant further investigation.

This discovery not only expands the applicable conditions of the Hall effect but also opens up new avenues for controlling quantum materials and spintronics.