Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets
| Autor: | A. Pantelica, Petru Palade, Aurel Leca, Ioan Dan, A.D. Crisan, O. Crisan |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Materials science
nanocomposite magnets Magnetometer Annealing (metallurgy) General Chemical Engineering Synchrotron radiation exchange coupling L10 FePt 02 engineering and technology 01 natural sciences Article mechanical alloying law.invention lcsh:Chemistry Condensed Matter::Materials Science law 0103 physical sciences General Materials Science 010302 applied physics Nanocomposite Condensed matter physics Coercivity 021001 nanoscience & nanotechnology SQUID lcsh:QD1-999 Remanence Magnet 0210 nano-technology |
| Zdroj: | Nanomaterials, Vol 10, Iss 1618, p 1618 (2020) Nanomaterials Volume 10 Issue 8 |
| ISSN: | 2079-4991 |
| Popis: | 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 Fe53Pt47 and Fe55Pt45, were subsequently annealed at 400 ° C and 550 ° C and structurally and magnetically characterized by means of X-ray diffraction, 57Fe Mö ssbauer spectrometry and Superconducting Quantum Interference Device (SQUID) magnetometry measurements. Gradual disorder&ndash 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 L10 phase is formed in both alloys, coexisting with a cubic L12 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&ndash soft exchange-coupled magnetic phases. |
| Databáze: | OpenAIRE |
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