Structural and magnetic properties of Nd-Fe-Mo-(N) melt-spun ribbons with ThMn12 structure
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Date
2020-06-03Author
Aubert, Alex
Madugundo, Rajasekhar
Saiz Garitaonandia, José Javier
Barandiarán García, José Manuel
Hadjipanayis, George C.
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Acta Materialia 195 : 519-526 (2020)
Abstract
The influence of quenching rate and nitrogenation in melt-spun Nd1.2Fe10.6Mo1.4 has been investigated in
terms of microstructure, phase formation and magnetic properties. Increasing the quenching rate leads
to smaller grain size. However, it also implies a change in the crystallized phase structure. We obtained
a pure ThMn12 (1:12) structure at quenching rates up to 30 m/s, leading to an average grain size of
220 nm. Magnetic measurements of the as-spun ribbons revealed a reduction of the saturation magneti zation for samples quenched above 30 m/s. This is attributed to the formation of a paramagnetic phase
and/or magnetic phase with a Curie temperature (TC) close to room temperature which is confirmed by 57Fe Mössbauer spectroscopy. The analysis of the spectra rules out the presence of a ferromagnetic TbCu7
(1:7) phase, which is usually reported in such system. The ribbons were nitrogenated in order to form
the harder magnetic phase Nd1.2Fe10.6Mo1.4Nx. The ribbon quenched at 30 m/s with the pure ThMn12 ni tride structure is the optimum sample for getting hard magnetic properties, with a coercivity of 0.6 T,
saturation magnetization of 1.15 T and Curie temperature of 350 °C. Finally, we show the good stability
of the later phase structure at elevated temperatures (≤ TC), making this compound a good candidate for
permanent magnet applications.