Effect of temperature and magnetic field on magnetomechanical damping of Fe-based bulk metallic glasses

Temperature and magnetic field dependence of magnetomechanical damping (MMD) of two ferromagnetic Fe-based bulk metallic glasses with different Curie temperatures, T C, have been studied over a broad temperature interval from the para-ferromagnetic transition down to 15 K. The damping has been scanned under periodic magnetic field at certain preselected temperatures in the ferromagnetic and paramagnetic phases. The selection of bulk metallic glasses for investigations allowed us to eliminate all dislocation-related anelastic effects and facilitated separation of the MMD components. Under zero field, the non-linear MMD emerges at T C and first increases linearly with (T C − T), then levels off until a maximum is formed at around 36 K. At lower temperatures, the magnetic domain wall related non-linear MMD component is partially or completely supressed, depending on the alloy composition. Qualitatively similar anomaly is found in the temperature dependence of the linear macroeddy current damping. These anomalies in the temperature spectra are concomitant with the emergence of a notable hysteresis in MMD versus periodic field dependences and of a maximum of non-linear MMD close to the position of the macroeddy damping peak. The uncovered phenomena are attributed to abrupt change of magnetic properties of ferromagnetic bulk metallic glasses at low temperatures, presumably due to the re-entrant spin glass transition.