Thermal stability, thermal expansion and grain-growth in exchange-coupled Fe–Pt–Ag–B bulk nanocomposite magnets

Nicula, R.; Crisan, O.; Crisan, A.; Mercioniu, I.; Stir, M.; Vasiliu, F.

doi:10.1016/j.jallcom.2014.10.181

Cited by 12 publications

(4 citation statements)

References 35 publications

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“…The thermal expansion is strongly anisotropic, being essentially an in-plane expansion. This is in agreement with the observed thermal expansion behavior of FeePteAgeB alloys [10]. The corresponding tetragonality ratio (c/a) is shown in Fig.…”

Section: As-cast Fe 35 Mn 15 Pt 50 Alloy Ribbonssupporting

confidence: 91%

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

Crisan

Mercioniu

et al. 2015

Intermetallics

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Section: As-cast Fe 35 Mn 15 Pt 50 Alloy Ribbonssupporting

confidence: 91%

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

Crisan

Mercioniu

et al. 2015

Intermetallics

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“…1B for low laser fluences suggests that expansive and contractive out-of-plane stresses have different time dependences. Although the thermal expansion of bulk FePt solid solutions of different composition has been studied (28)(29)(30)(31), static characterization of the out-of-plane expansion for continuous and granular L1 0 -ordered thin films approaching the Curie temperature T C ≈ 700 K was, so far, not available. Our results in Fig 1C show that the out-of-plane dimension of L1 0 -FePt behaves invar-like for the continuous film and even exhibits negative thermal expansion (NTE) for the granular FePt sample.…”

Section: Time-resolved and Static Expansionmentioning

confidence: 99%

Spin stress contribution to the lattice dynamics of FePt

et al. 2020

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Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments. We show that the granular microstructure is essential to support the contractive out-of-plane stresses originating from in-plane expansion via the Poisson effect that add to the uniaxial contractive stress driven by spin disorder. We prove the spin contribution by saturating the magnetic excitations with a first laser pulse and then detecting the purely expansive response to a second pulse. The contractive spin stress is reestablished on the same 100-ps time scale that we observe for the recovery of the ferromagnetic order. Finite-element modeling of the mechanical response of FePt nanosystems confirms the morphology dependence of the dynamics.

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“…Stoichiometry not only plays a role in forming the τ-MnAl, but microstructural arrangements of grains also play a role upon casting the alloy and the thermodynamic equilibrium. The similarity of the tetragonal τ-phase with the superlattice features of other L1 0 phases has also been reported [15][16][17][18][19][20]. Two main pathways for obtaining τ-MnAl have been reported [21,22]: (a) ultra-rapid quench of equilibrium ε-phase successively followed by thermal treatment and (b) slow cooling of the parent disordered ε-phase.…”

Section: Introductionmentioning

confidence: 60%

Thermal Stability, Blocking Regime and Superparamagnetic Behavior in Mn-Al-C Melt Spun Ribbons

et al. 2021

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Alloys possessing nominal compositions Mn53Al45C2 and Mn52Al46C2 were prepared by the melt spinning method and were subjected to complex structural, morphological and magnetic investigations. As these alloys can exhibit tetragonal L10-type and τ phase, they have good potential as rare earth (RE)—free magnets. It is, therefore, important to monitor the ε–τ phase transformation and the stability and the magnetic features of the tetragonal phase in an entire temperature interval. By using synchrotron X-ray diffraction, it has been proven that the ε–τ phase transformation occurs gradually, with the τ phase becoming predominant only after 450 °C. Moreover, this phase has been proven to be quite stable without any grain growth even at the highest temperature investigated at 800 °C. Low temperature behavior was thoroughly investigated by using a complex combination of major and minor hysteresis loops combined with the zero field cooled-field cooled magnetization protocols (ZFC-FC). Two different regimes, blocking and superparamagnetic, were documented. A spin reorientation transition was proven to occur at 55 K while a maximum magnetization observed in ZFC-FC curves proved that at about 75 K, a transition from ferro to superparamagnetic state occurs. The existence of a blocking regime below 55 K that is characteristic to nanogranular systems with superparamagnetic behavior has shown further development towards obtaining RE-free magnets.

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Thermal stability, thermal expansion and grain-growth in exchange-coupled Fe–Pt–Ag–B bulk nanocomposite magnets

Cited by 12 publications

References 35 publications

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

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

Spin stress contribution to the lattice dynamics of FePt

Thermal Stability, Blocking Regime and Superparamagnetic Behavior in Mn-Al-C Melt Spun Ribbons

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