Takumi Funato, a Project Assistant Professor at the Global Research Institute at Keio University (Spintronics Research and Development Center), and Mamoru Matsuo, an Associate Professor at the Kavli Institute for Theoretical Science at the Chinese Academy of Sciences, have theoretically demonstrated that the gyromagnetic effect induces electromotive force when sound waves are injected into magnets. The gyromagnetic effect, discovered by Einstein and de Haas and Barnett, is a historically significant phenomenon indicating that the origin of magnetism in matter is the rotation of electrons called "spin."
The gyromagnetic effect, however, is so small that it was considered impossible to apply to spintronics devices, where magnetic control of materials is essential. In a recent experiment, researchers demonstrated that it is possible to generate spin current via the gyromagnetic effect by utilizing sound waves to rotate lattices more than a billion times per second. Researchers have also discovered methods to convert the spin currents into charge currents; however, they require sophisticated device structures and precious metals. To overcome these limitations, the research group in this study theoretically clarified the interplay of magnetization, electron spin, and lattice rotation in ferromagnetic metal monolayers, where injected sound waves induce lattice rotational motion.
The researchers demonstrated that the gyromagnetic effect could induce electromotive force with a simple device structure. The mechanism discovered in this study is expected to significantly contribute to applications of the gyromagnetic effect in spin devices, which has been difficult so far. The results of this research were published online in the American physics journal Physical Review Letters on February 18, 2022 (Eastern Standard Time).