Carnegie Mellon University physicists have experimentally demonstrated a new form of the Hall effect, challenging the long-held assumption that the phenomenon requires a magnetic field perpendicular to a material. The discovery could lead to simpler magnetic sensors capable of detecting fields in multiple directions using a single device.
The Hall effect, discovered by Edwin Hall in 1879, occurs when a magnetic field deflects moving electrical charges and generates a measurable voltage. It has become an important method for studying electronic materials and underpins sensors used in applications ranging from automobiles to computer keyboards.
Researchers at Carnegie Mellon’s Lab for Investigating Quantum Materials, Interfaces, and Devices demonstrated that a Hall response can also occur when magnetization lies within the plane of a material. Although scientists had theoretically proposed this in-plane anomalous Hall effect, producing a material with the required symmetry had remained difficult.
The researchers created nanometer-scale devices using tantalum iridium telluride, or TaIrTe4, a material possessing the necessary crystalline symmetry. They reduced it to a few atomic layers and combined it with a magnetic material called Cr2Ge2Te6, or CGT. Proximity between the materials induced magnetic properties in the normally nonmagnetic TaIrTe4 while retaining its electronic characteristics.
Experiments revealed both the conventional Hall signal and an additional signal associated with in-plane magnetization. This means one ultrathin device could potentially measure magnetic fields along multiple axes, replacing configurations that currently require multiple sensors.
Theoretical modeling indicated that reduced symmetry created by combining the materials enables additional spin-orbit coupling at their interface, helping produce the unusual Hall response at low temperatures.
Researchers are now investigating other materials that could exhibit the effect and testing whether the devices can operate at room temperature, a critical requirement for practical sensing applications.
