The anomalous Hall effect is a phenomenon that occurs in magnetic materials, particularly in ferromagnetic materials where electron spins are aligned. When an electric current flows through a metal sample in a magnetic field, it experiences the Lorentz force, generating a voltage perpendicular to the magnetic field and current. This effect, known as the Hall effect, is well-understood. However, the anomalous Hall effect can occur independently of an external magnetic field, manifesting below a certain temperature called the magnetic transition temperature.
A research group from the University of Tsukuba has made a significant discovery regarding electron spins in magnetic materials. They found that fluctuations of electron spins in materials undergoing a phase transition, known as the devil’s staircase magnetic transition, can trigger a large anomalous Hall effect. This finding is crucial for the advancement of magneto-thermoelectric conversion, a technology aimed at generating power in an environmentally friendly manner.
In their study published in npj Quantum Materials, the researchers observed a large anomalous Hall effect at temperatures above the magnetic transition temperature in the magnetic material SrCo6O11. This material exhibits a unique magnetic transition phenomenon called the “spin-fluctuating devil’s staircase.” The researchers noted that the magnitude of the anomalous Hall effect, also known as the anomalous Hall angle, was one of the largest ever recorded for magnetic oxides.
The researchers believe that the significant anomalous Hall effect observed in SrCo6O11 is due to intense scattering of conduction electrons caused by a specific type of spin fluctuation called spin-flip fluctuation. This discovery opens up new possibilities for the design of materials for magneto-thermoelectric conversion technology. The development of new thermoelectric conversion materials could be greatly influenced by these findings.
The research conducted by the University of Tsukuba’s team sheds light on the role of electron spin fluctuations in triggering large anomalous Hall effects during phase transitions in magnetic materials. This groundbreaking discovery paves the way for advancements in magneto-thermoelectric conversion technology and the development of new materials with enhanced thermoelectric capabilities.