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Crystallization processes and phase evolution in amorphous Fe–Pt–Nb–B alloys

Domenii publicaţii > Fizica + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Ovidiu Crisan, Alina-Daniela Crisan, Nirina Randrianantoandro, Radu Nicula and Eberhard Burkel

Editorial: Elsevier Science, Journal of Alloys and Compounds, DOI:10.1016/j.jallcom.2006.08.331, p.in print, 2006.

Rezumat:

Fe–Pt system is nowadays widely studied due to its potential applications as magnetic recording media. The hard magnetic FePt L10 phase has extremely promising potential as permanent magnet with high magnetocrystalline anisotropy. Of recent interest is also the developing of the hard magnetic phase from an amorphous precursor by appropriate crystallization processes. The melt-spun amorphous Fe68Pt13Nb2B17 alloy has been submitted to dynamical annealing and its phase transformation during the process has been monitored by differential scanning calorimetry and in situ energy-dispersive X-ray diffraction of the synchrotron radiation. In the first stage of crystallization, α-Fe and cubic FePt phases are formed from the amorphous precursor. At around 600 °C superlattice Bragg reflections corresponding to tetragonal FePt are indexed in the XRD spectra and α-Fe phase diminishes drastically. Finally, between 900 °C and 975 °C the tetragonal superlattice peaks disappear and cubic FePt phase is formed again. This reversible order–disorder transformation is accompanied by a strong uniaxial lattice expansion of the cubic FePt unit cell. The system show promising features for the co-existence of hard and soft exchange coupled magnetic phases crystallized from FePt-based amorphous precursors.

Cuvinte cheie: Magnetically ordered materials; Thermal analysis; Rapid solidification; X-ray diffraction