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Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets

With the aim of demonstrating phase coexistence of two magnetic phases in an intermediate annealing regime and obtaining highly coercive FePt nanocomposite magnets, two alloys of slightly off-equiatomic composition of a binary Fe-Pt system were prepared by dynamic rotation switching and ball milling...

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Autores principales: Crisan, O., Dan, I., Palade, P., Crisan, A. D., Leca, A., Pantelica, A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7466679/
https://www.ncbi.nlm.nih.gov/pubmed/32824779
http://dx.doi.org/10.3390/nano10081618
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author Crisan, O.
Dan, I.
Palade, P.
Crisan, A. D.
Leca, A.
Pantelica, A.
author_facet Crisan, O.
Dan, I.
Palade, P.
Crisan, A. D.
Leca, A.
Pantelica, A.
author_sort Crisan, O.
collection PubMed
description With the aim of demonstrating phase coexistence of two magnetic phases in an intermediate annealing regime and obtaining highly coercive FePt nanocomposite magnets, two alloys of slightly off-equiatomic composition of a binary Fe-Pt system were prepared by dynamic rotation switching and ball milling. The alloys, with a composition Fe(53)Pt(47) and Fe(55)Pt(45), were subsequently annealed at 400 °C and 550 °C and structurally and magnetically characterized by means of X-ray diffraction, (57)Fe Mössbauer spectrometry and Superconducting Quantum Interference Device (SQUID) magnetometry measurements. Gradual disorder–order phase transformation and temperature-dependent evolution of the phase structure were monitored using X-ray diffraction of synchrotron radiation. It was shown that for annealing temperatures as low as 400 °C, a predominant, highly ordered L1(0) phase is formed in both alloys, coexisting with a cubic L1(2) soft magnetic FePt phase. The coexistence of the two phases is evidenced through all the investigating techniques that we employed. SQUID magnetometry hysteresis loops of samples annealed at 400 °C exhibit inflection points that witness the coexistence of the soft and hard magnetic phases and high values of coercivity and remanence are obtained. For the samples annealed at 500 °C, the hysteresis loops are continuous, without inflection points, witnessing complete exchange coupling of the hard and soft magnetic phases and further enhancement of the coercive field. Maximum energy products comparable with values of current permanent magnets are found for both samples for annealing temperatures as low as 500 °C. These findings demonstrate an interesting method to obtain rare earth-free permanent nanocomposite magnets with hard–soft exchange-coupled magnetic phases.
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spelling pubmed-74666792020-09-14 Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets Crisan, O. Dan, I. Palade, P. Crisan, A. D. Leca, A. Pantelica, A. Nanomaterials (Basel) Article With the aim of demonstrating phase coexistence of two magnetic phases in an intermediate annealing regime and obtaining highly coercive FePt nanocomposite magnets, two alloys of slightly off-equiatomic composition of a binary Fe-Pt system were prepared by dynamic rotation switching and ball milling. The alloys, with a composition Fe(53)Pt(47) and Fe(55)Pt(45), were subsequently annealed at 400 °C and 550 °C and structurally and magnetically characterized by means of X-ray diffraction, (57)Fe Mössbauer spectrometry and Superconducting Quantum Interference Device (SQUID) magnetometry measurements. Gradual disorder–order phase transformation and temperature-dependent evolution of the phase structure were monitored using X-ray diffraction of synchrotron radiation. It was shown that for annealing temperatures as low as 400 °C, a predominant, highly ordered L1(0) phase is formed in both alloys, coexisting with a cubic L1(2) soft magnetic FePt phase. The coexistence of the two phases is evidenced through all the investigating techniques that we employed. SQUID magnetometry hysteresis loops of samples annealed at 400 °C exhibit inflection points that witness the coexistence of the soft and hard magnetic phases and high values of coercivity and remanence are obtained. For the samples annealed at 500 °C, the hysteresis loops are continuous, without inflection points, witnessing complete exchange coupling of the hard and soft magnetic phases and further enhancement of the coercive field. Maximum energy products comparable with values of current permanent magnets are found for both samples for annealing temperatures as low as 500 °C. These findings demonstrate an interesting method to obtain rare earth-free permanent nanocomposite magnets with hard–soft exchange-coupled magnetic phases. MDPI 2020-08-18 /pmc/articles/PMC7466679/ /pubmed/32824779 http://dx.doi.org/10.3390/nano10081618 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Crisan, O.
Dan, I.
Palade, P.
Crisan, A. D.
Leca, A.
Pantelica, A.
Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets
title Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets
title_full Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets
title_fullStr Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets
title_full_unstemmed Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets
title_short Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets
title_sort magnetic phase coexistence and hard–soft exchange coupling in fept nanocomposite magnets
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7466679/
https://www.ncbi.nlm.nih.gov/pubmed/32824779
http://dx.doi.org/10.3390/nano10081618
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