Magnetomechanische Verstärkung und Erzeugung mechanischer Schwingungen

A torsional pendulum with a Nickel-rod as torsional spring element can oscillate in its eigenfrequency when the rod is magnetized in its axial direction by an ac magnetic field. Investigating this effect, which was not understood until now, a mechanism of parametric amplification and generation of mechanical vibrations is derived. It is based on the effect of Joule's magnetostriction and its inverse. The calculations presented enable us to understand the experimental results of the corresponding oscillation measurements.