Phase transformations and thermodynamic properties of nanocrystalline FePt powders

Lyubina, Julia; Gutfleisch, Oliver; Skomski, Ralph; Müller, K.‐H.; Schultz, L.

doi:10.1016/j.scriptamat.2005.04.041

Cited by 27 publications

(10 citation statements)

References 18 publications

(24 reference statements)

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“…Furthermore, the ordering kinetics was found to be enhanced for the fine lamellar structure of Fe/FePt(A1)/Pt. [24] Annealing of the 2 h milled Fe 100-x Pt x (x = 39.5; 45; 50; 55; 60) powders with the lamellar microstructure induces immediate formation and ordering of L1 0 FePt, the maximum amount of which is about 85 vol.% for Fe 50 Pt 50 after annealing at 450 C/48 h. As an example, Figure 4 shows the x-ray diffraction pattern of this powder. Rietveld refinement of the x-ray data reveals the presence and allows the quantification of additional phases such as A1 FePt, Fe 3 Pt (L1 2 ) and FePt 3 (L1 2 ), additionally to the L1 0 phase.…”

Section: Resultsmentioning

confidence: 99%

FePt Hard Magnets

et al. 2005

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The FePt alloys have recently attracted considerable attention due to their excellent intrinsic magnetic, chemical and mechanical properties. Their possible usage ranges from permanent magnets for special applications (e.g. in micro‐electro‐mechanical systems, magnetic MEMS, and in aggressive environments) to ultra‐high density magnetic storage media. The article describes general aspects concerning the phase formation and magnetic properties of materials based on the L10 FePt phase. Both thin film and bulk approaches are considered. The production of bulk nanocrystalline Fe100‐xPtx powders by mechanical alloying and subsequent annealing is described. Various combinations of phases, away from thermodynamic equilibrium, have been obtained using this technique.

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Section: Resultsmentioning

confidence: 99%

FePt Hard Magnets

et al. 2005

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“…Milling at low temperatures has the advantage of reducing the cold welding of ductile metals [17] such as Mg to the milling media. In addition, a smaller average grain size, a larger strain distribution and an extended solid solubility are expected [18], creating more favourable hydriding conditions.…”

Section: Introductionmentioning

confidence: 99%

Hydride formation in ball-milled and cryomilled Mg–Fe powder mixtures

Riktor

Deledda

Herrich

et al. 2009

Materials Science and Engineering: B

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“…Calorimetric studies of the A1 to L1 0 transition in FePt particles have revealed that the activation energy of phase transformation is about 1.0-1.7 eV. [26][27][28] A diffusion distance x is given as …”

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confidence: 99%

Rapid thermal annealing of FePt nanoparticles

Yano

Nandwana

Poudyal

et al. 2008

Journal of Applied Physics

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We report a systematic study on rapid thermal annealing ͑RTA͒ of FePt nanoparticles. FePt particles with an average size of 8 nm were synthesized by a chemical solution method, and then annealed using RTA and conventional furnace annealing ͑FA͒. It was observed that FePt nanoparticles can be transformed from disordered A1 phase to ordered L1 0 phase at 650°C for 10 s using RTA, which is much shorter than the time needed for FA. The transmission electron microscopy and x-ray diffraction studies have revealed that the particle agglomeration and grain growth in the RTA treated samples are much less than in the FA treated samples. A linear correlation between the coercivity and the square root of the treatment time ͱ t was observed in the RTA treated samples, which implies that the phase transition is related to atomic diffusion of Fe atoms from Fe-rich shells into the Pt-rich cores.

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Phase transformations and thermodynamic properties of nanocrystalline FePt powders

Cited by 27 publications

References 18 publications

FePt Hard Magnets

FePt Hard Magnets

Hydride formation in ball-milled and cryomilled Mg–Fe powder mixtures

Rapid thermal annealing of FePt nanoparticles

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