Vibrating ferromagnets in a magnetic field

With the vibrating reed technique we have studied the magnetoelastic behavior and the dynamical response of amorphous and crystalline magnets in the ferromagnetic and re-entrant spin glass states. The measurements have been performed as a function of magnetic field, temperature and angle between the sampleʹs main area and the applied field. The resonance frequency of the reed is influenced by a static contribution (pole effect), a dynamic contribution with a large effect due to the pinning of magnetic domains and magnetostrictive effects. When the field is applied perpendicular to the main area of the sample, a large decrease of the resonance frequency is observed which is rather independent of the material characteristics and is not related to a change of the Young modulus. A field misalignment of a few degrees strongly affects the field dependence of the resonance frequency. We briefly discuss the influence of the re-entrant spin glass state on the magnetoelastic behavior and the characteristics of the internal friction of vibrating ferromagnets in a magnetic field.