Electromagnetic generation of 9.4-GHz phonons in Fe and Ni

Abstract

The conversion of microwaves to phonons has been observed and studied in thick iron and nickel single crystal and polycrystalline films. The experiments were of the transmission type with the sample forming part of the common wall between two microwave cavities. Sound is generated in the presence of a static magnetic field by the Lorentz force, causing the electronic current to drive the lattice. The sound amplitude, which is enhanced in certain field configurations by the sample’s magnetization, is essentially field independent after saturation for applied fields of the order of 10 kOe and increases as the temperature decreases from room temperature to 77 K. These results explain previously misinterpreted observations in iron, nickel, and other ferromagnetic metals. High frequency constant amplitude sound could be used as a tool to study the electronic properties of ferromagnetic metals.