The metal gold was considered to be magnetic for a long time. A team of researchers from Tohoku University recently found that gold can be magnetized when heated. The team discovered that an electron spin can be responsible for a material’s functionality for non-constant temperatures, where the interaction between magnetization and heat flows can occur. A subsequent experiment confirmed for the first time that a temperature change can induce a magnetization in gold.
We used an insulating magnet, Yttrium iron garnet (YIG), as well as a thin film of gold for the experiment, which was quite simple to set up. This is illustrated in the figure below. For this experiment, the temperature of the gold side of the bilayer was set higher than that of the YIG side to force heat to flow in a perpendicular direction. Further, in parallel with the heat flow, a magnetic field was applied. In this case, the Hall voltage*1 was measured by measuring the in-plane electric current through the gold film. According to the Hall voltage, the applied temperature gradient had a clear proportional effect. During heat flow, a Hall voltage appeared in the thin gold film. This created evidence of the evolution of magnetization within the thin gold film. An anomalous Hall effect (nAHE) has been named for the non-equilibrium Hall voltage. Dazhi Hou, a researcher at Jiangnan University, says that this measurement may be used as a standard method of detecting non-equilibrium magnetization, since it requires no complicated processing or technological advances compared to other highly sensitive magnetometers. On top of that, we can detect magnetization that is so small that it cannot be detected by any other method. The tiny magnetizations described here may uncover details about the properties of matter that are yet to be revealed.” “These findings are expected to help develop thermoelectric applications, including energy harvesting, in spintronics,” says Professor Eiji Saitoh, who led the study. The details of this study were published online in Nature Communications on July 26, 2016. As a result of a JST-ERATO “Spin Quantum Rectification Project” lead by Professor Eiji Saitoh, this research has been achieved. As an electrical current flows through a conductor and a magnetic field is imposed perpendicularly to the direction of the current, an electric voltage will result in a direction perpendicular to both