Magnetization control by angular momentum transfer from surface acoustic wave to ferromagnetic spin moments*

An angular momentum interconversion between electron spin and other types of angular momentum is useful for developing new spintronic functionalities. The conversions from photon angular momentum and mechanical rotation to ferromagnetic spin moment have been well studied. Although recent studies theoretically suggested that circular vibration of atoms may work as phonon angular momentum, a direct experimental demonstration of conversion to spin moments remains to be performed.
Here we demonstrate that the phonon angular momentum of surface acoustic wave can control the magnetization of a ferromagnetic Ni film by means of the phononic-to-electronic conversion of angular momentum in a Ni/LiNbO₃ hybrid device. The result clearly shows that the phonon angular momentum is useful for increasing the functionality of spintronic devices.