Temperature Evolution of Magnetic Structure in Fe-Co-Si-B-Mo-P Metallic Glass by Mossbauer Spectrometry

Magnetic ordering in Fe51Co12Si16B8Mo5P8 metallic glass is followed by Fe-57 transmission Mossbauer spectrometry performed at temperatures ranging from 4.2 K up to 415 K. Low temperature experiments were accomplished also in external magnetic field of 6 T oriented parallel to the ribbon plane. Evolution of Mossbauer spectra with sample temperature shows gradual vanishing of hyperfine magnetic fields. High temperature Mossbauer spectra exhibit clear transition from ferromagnetic to paramagnetic state. In this way, the Curie temperature can be determined. We have concentrated on samples annealed at 573 K and 673 K, i.e., well below the onset of crystallization. Measurements at 4.2 K revealed rearrangement of spins that is taking place both after the annealing, as well as in external magnetic field. From high temperature experiments, the Curie temperature of 400 K was determined for the sample annealed at 673 K.