Superparamagnetic behaviour of Fe80B12Zr7Cu alloys with different fractions of primary nanocrystalline phase

The superparamagnetic behaviour of nanocrystalline (nc) Fe80B12Zr7Cu alloys, having different amounts of body centred cubic (bcc) fraction controlled by DSC heat treatments was studied by high temperature SQUID magnetometry and Mِssbauer spectroscopy. The granule diameter calculated from magnetic measurements is significantly higher than the X-ray determined grain size but is proportional to that value. The superparamagnetic behaviour is observed at substantially lower temperatures by the Mِssbauer spectroscopy than by the macroscopic magnetisation studies, which means that the applied magnetic field significantly influences the superparamagnetic behaviour.