Generation of Gigahertz phonons in dysprosium films

A tuneable spin‐phonon spectrometer has been used to investigate the generation of microwave phonons in films of dysprosium for frequencies varying from 10–32 GHz. The films, whose thicknesses were varied from .5 to 2.4 μM, were evaporated onto one end of the phonon detector, a rectangular rod of SrF2 doped with Tm++. Static and rf magnetic fields were applied in the plane of the sample, and in addition to biasing the sample, the static field was used to tune the spectrometer. A simple analysis, based on the free lattice model proposed to describe dynamic magnetoelastic effects in rare earth metals, shows that phonons should be generated at the rf field frequency, νo, and with a smaller intensity at 2 νo. Phonons at νo have been extensively studied and it was found that the phonon signal depends on the intensity of the rf field, as would be expected, but is very insensitive to the angle between the rf and static fields. Evidence exists for broad phonon generation at 2 νo.