Abstract
In order to prove the usefulness of having a structurally disordered precursor to the formation of FePt L10 phase and to facilitate the co-existence of exchange coupled hard and soft magnetic phases with optimized magnetic properties in various conditions of annealing, a Fe-Pt-Zr-B melt spun alloy has been synthesized and detailed structural and magnetic investigations have been undertaken to probe its phase evolution during annealing. The dynamics of formation of the hard magnetic L10 phase during the gradual disorder–order phase transformation has been monitored by using a complex combination of X-ray diffraction methods and 57Fe Mössbauer spectroscopy methods, over a wide range of annealing temperatures. Multiple phases co-existing in the annealed sample microstructures, observed in XRD, have been reconfirmed by the Mössbauer spectra analysis and, moreover, accurate quantitative data have been acquired in what concerns the relative abundance of each of the observed crystalline phases in every stage of annealing. It is shown that the formation of the hard magnetic phase, emerging from the chemically disordered precursor, is gradual and occurs via complex mechanisms, involving the presence of a disordered Fe-Zr-B-rich intergranular region which contributes to an increase in the abundance of the L10 phase for higher annealing temperatures. Magnetic measurements have confirmed the good performances of these alloys in terms of coercivity and remanence. These results contribute to the development of these alloys as the next generation of rare earth, free permanent magnets.
Highlights
Another way to create magnetic alloys with good magnetic properties is to achieve a hard–soft magnetic structure, where the hard magnetic FePt phase is exchange-coupled to soft magnetic ones, and to take full advantage from the high magnetization of the soft phase and the high coercivity of the hard magnetic phase, in order to maximize the energy product (BH)max
The hyperfine field (HF) parameters obtained are consistent with the results reported in the literature [36] and with those obtained from the investigation on the as-cast sample
We have synthesized a nanocomposite magnet based on the FePt-Zr-B alloy, by using the non-equilibrium melt spinning method
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Non-equilibrium synthesis methods are appropriate for achieving the formation of an L10 phase in melt-spun FePt-based ribbons without the need for post-synthesis annealing [2] Another way to create magnetic alloys with good magnetic properties is to achieve a hard–soft magnetic structure, where the hard magnetic FePt phase is exchange-coupled to soft magnetic ones, and to take full advantage from the high magnetization of the soft phase and the high coercivity of the hard magnetic phase, in order to maximize the energy product (BH)max. The present work is dedicated to the detailed structural and morphological study of the microstructure modifications and phase evolution during annealing, as well as the magnetic properties of a Fe-Pt-Zr-B melt-spun alloys, co-existence of exchange coupled hard and soft magnetic phases and the magnetic properties in various conditions of annealing
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