Study of Magnetic Materials by Mössbauer Thermal Scans. Application to Nanocrystalline Systems

F.H. SÁNCHEZ, G. PASQUEVICH, P.MENDOZA ZÉLIS, A.F. CABRERA, LIN AND M. VÁZQUEZ

JOURNAL OF METASTABLE AND NANOCRYSTALLINE MATERIALS

Año: 2004 vol. 22 p. 39 - 44

1422-6375

Mössbauer thermal scans (2 K/min) have been applied to the classical amorphous finemet-type precursor Fe73.5Si13.5Nb6Cu1B9 alloy. They allowed the determination of the ordering temperatures of the amorphous phase before (TC = 624 K) and after partial (TC = 674 K) and complete (TC = 595 K) crystallization. The existence of three well differentiated temperature regions is observed,  corresponding to the ferro to paramagnetic transition of the amorphous, nanocrystallization of bcc Fe(Si) and the ferro to superpara or paramagnetic transition of the crystalline phase. The crystallization kinetics at 763 K and 805 K was studied by two different approaches. At 763 K spectra were recorded every two hours up to a total time of 117 h. At 805 K scans were used due to the much higher transformation rate. Both results were analized with theoretical contributions representing the amorphous, very small crystals or embryos and grown up crystals. The evolution of their relative abundances obtained with the two approaches was consistent. The embryo nucleation was almost completed after two and eight hours at 763 and 805 K, respectively.