Effect of Mn addition on the thermal stability and magnetic properties of rapidly-quenched L10 FePt alloys

Crisan, O.; Crisan, A.; Mercioniu, I.; Pantelică, D.; Pantelica, A.; Vaucher, S.; Nicula, R.; Stir, M.; Vasiliu, F.

doi:10.1016/j.intermet.2015.06.008

Cited by 8 publications

(6 citation statements)

References 28 publications

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“…As a consequence, we note that the thermal expansion of the tetragonally distorted unit cell is strongly anisotropic, occurring essentially in-plane. This phenomenon has also been observed in ternary L10 phases in Fe-Mn-Pt [38] and is in agreement with thermal expansion behavior of Fe-Pt-Ag-B alloys [39]. The corresponding tetragonality ratio (c/a) is shown also in Figure 5.…”

Section: Resultssupporting

confidence: 87%

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

et al. 2020

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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 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 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–soft exchange-coupled magnetic phases.

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Section: Resultssupporting

confidence: 87%

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

et al. 2020

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“…It is worth noting that the formation of τ-phase in Mn-Al depends strongly upon stoichiometry, microstructural details, as well as thermodynamic considerations. As said above, the ferromagnetic τ-phase has a tetragonal superlattice structure that is similar to other L1 0 phases [ 15 , 16 , 17 , 18 , 19 , 20 ]. It has been reported [ 21 , 22 ] that τ-MnAl is synthesized either by the rapid quenching of ε-phase and subsequent annealing or by slowly cooling down the parent disordered ε-phase.…”

Section: Introductionmentioning

confidence: 69%

Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets

et al. 2021

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Melt spun ribbons of Mn53Al45C2 and Mn52Al46C2 have been synthesized by rapid quenching of the melt with the purpose of monitoring the ε-τ phase transformation to show technologically feasible ways to increase magnetic parameters and to illustrate the viability of these alloys as the next generation of rare earth (RE)-free magnets. By differential scanning calorimetry (DSC), activation energies and temperatures of onset of the ε-τ phase transformation were obtained. Structural analysis was performed using X-ray diffraction (XRD) and the resulting XRD patterns were quantitatively assessed using full profile Rietveld-type analysis. Appropriate annealing was performed in order to enable the ε-τ phase transformation. While hcp ε-phase was found to be predominant in the as-cast samples, after appropriate annealing, the tetragonal τ-phase, the one that furnishes the relevant magnetic response, was found to be predominant with an abundance of about 90%. The data suggested a mechanism of hcp ε-phase decomposition controlled by the segregation towards the interfacial regions, having the rate of transformation governed by antiphase boundary diffusion processes. Magnetic measurements of annealed sample Mn53Al45C2, consisting of predominant tetragonal τ-phase, showed high values of magnetization and increased coercivity, consistent with an energy product of about 10 MGOe, similar with previously reported magnetization measurements, providing further insight into the realization of future class of RE-free low-cost permanent magnets.

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“…Due to slight lattice distortion, the unit cell of ternary L1 0 phase would be different from its binary counterpart. In fact, co-existence of the two L1 0 phases, binary and ternary, has been observed through atomic resolution TEM and electron diffraction patterns [ 6 ] in other FeMnPt alloys.…”

Section: Resultsmentioning

confidence: 99%

“…A technological barrier that impedes the adoption of such systems is related to the fact that the tetragonal, hard magnetic L1 0 , the phase of interest, is only formed after post-synthesis annealing of the alloys [ 4 ]. Several attempts to circumvent this barrier included slight stoichiometry changes in the initial binary alloys or the addition of several elements such as Ag [ 5 ], Mn [ 6 ] and B [ 7 ]. We have shown [ 5 ] that adding both Ag and B to the binary FePt alloy led to the direct formation of L1 0 phase, with high coercivity and without the need for post-synthesis annealing of as-cast alloys.…”

Section: Introductionmentioning

confidence: 99%

“…We have shown [ 5 ] that adding both Ag and B to the binary FePt alloy led to the direct formation of L1 0 phase, with high coercivity and without the need for post-synthesis annealing of as-cast alloys. We have also previously shown that Mn addition in small amounts (36 at%) creates better stability of L1 0 phase, and moreover, it promotes the occurrence of both binary FePt and ternary FeMnPt L1 0 phases, making the alloys highly coercive [ 6 , 8 ]. Several other works reported show the intense focus on these alloys, as a pertinent alternative for the RE permanent magnets [ 9 , 10 , 11 , 12 , 13 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

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Mn-Induced Thermal Stability of L10 Phase in Fept Magnetic Nanoscale Ribbons

Crisan

Leca

Pantelică³

et al. 2020

Nanomaterials

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Magnetic nanoscale materials exhibiting the L10 tetragonal phase such as FePt or ternary alloys derived from FePt show most promising magnetic properties as a novel class of rare earth free permanent magnets with high operating temperature. A granular alloy derived from binary FePt with low Pt content and the addition of Mn with the nominal composition Fe57Mn8Pt35 has been synthesized in the shape of melt-spun ribbons and subsequently annealed at 600 °C and 700 °C for promoting the formation of single phase, L10 tetragonal, hard magnetic phase. Proton-induced X-ray emission spectroscopy PIXE has been utilized for checking the compositional effect of Mn addition. Structural properties were analyzed using X-ray diffraction and diffractograms were analyzed using full profile Rietveld-type analysis with MAUD (Materials Analysis Using Diffraction) software. By using temperature-dependent synchrotron X-ray diffraction, the disorder–order phase transformation and the stability of the hard magnetic L10 phase were monitored over a large temperature range (50–800 °C). A large interval of structural stability of the L10 phase was observed and this stability was interpreted in terms of higher ordering of the L10 phase promoted by the Mn addition. It was moreover found that both crystal growth and unit cell expansion are inhibited, up to the highest temperature investigated (800 °C), proving thus that the Mn addition stabilizes the formed L10 structure further. Magnetic hysteresis loops confirmed structural data, revealing a strong coercive field for a sample wherein single phase, hard, magnetic tetragonal L10 exists. These findings open good perspectives for use as nanocomposite, rare earth free magnets, working in extreme operation conditions.

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Effect of Mn addition on the thermal stability and magnetic properties of rapidly-quenched L10 FePt alloys

Cited by 8 publications

References 28 publications

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

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

Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets

Mn-Induced Thermal Stability of L10 Phase in Fept Magnetic Nanoscale Ribbons

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