Magnetoacoustic Excitation of Radio-Frequency Resonances and Echoes in Magnetic Materials

Continuous spectra of resonances are observed when some ferromagnetic substances are examined with cw or spin-echo rf spectrometers. These resonances have previously been assigned to domain-wall motion; evidence is presented here to show rather that they are magnetically excited acoustic vibrations. An explanation of the manner in which a nonlinear magnetoacoustic interaction allows the production of echoes in an otherwise linear system is presented. A means of suppressing these resonances to facilitate the study of nuclear magnetic resonances in magnetic materials is demonstrated.