Frédéric Mazaleyrat

X-ray diffraction analysis of the magnetoelastic phase transition in the Mn-Fe-P-Si magnetocaloric alloy

Structural characterization of the Mn1.3Fe0.65P0.5Si0.5 powder is reported. The rare-earth-free magnetocaloric material was prepared by ball milling and solid-state synthesis. X-ray diffraction data were collected in a wide temperature range across the magnetoelastic phase transition. The lattice parameters and volume fractions of the paramagnetic and ferromagnetic phases were determined as functions of temperature using Rietveld fitting. The virgin effect (a delay of the phase transition on first cooling) and associated variation of lattice parameters are analyzed on the assumption of elastic constraints imposed on the paramagnetic phase by the defect structure. A simple Landau model with magnetoelastic coupling illustrates the observed first-order behavior.

Mg1-xZnxFe2O4 nanoparticles: Interplay between cation distribution and magnetic properties

Correlation between cationic distribution, magnetic properties of Mg1-xZnxFe2O4 (0.0 ≤ x ≤ 1.0) ferrite is demonstrated, hardly shown in literature. X-ray diffraction (XRD) confirms the formation of cubic spinel nano ferrites with grain diameter between 40.8 to 55.4 nm. Energy dispersive spectroscopy (EDS) confirms close agreement of Mg/Fe, Zn/Fe molar ratio, presence of all elements (Mg, Zn, Fe, O), formation of estimated ferrite composition. Zn addition (for Mg) shows: i) linear increase of lattice parameter aexp, accounted for replacement of an ion with higher ionic radius (Zn > Mg); ii) presence of higher population of Fe3+ ions on B site, and unusual occurrence of Zn, Mg on A and B site leads to non-equilibrium cation distribution where we observe inverse to mixed structure, and is in contrast to reported literature where inverse to normal transition is reported; iii) effect on A-A, A-B, B-B exchange interactions, affecting coercivity Hc, Ms. A new empirical relation is also obtained showing linear r...

First- Versus Second-Order Magnetocaloric Material for Thermomagnetic Energy Conversion

We estimate the power and efficiency of a thermal energy harvesting thermodynamic Brayton cycle using the first- and second-order magnetocaloric materials as active substance. The thermodynamic cycle was computed using a simple thermal exchange model and an equation of the state deduced from a phenomenological Landau model. For the first- and second-order materials, narrow- and high-frequency cycles are optimum and give similar performances. Considering technological issues hindering the increase of frequency, we introduced a more detailed approach, where we take into account the time needed to switch the material between two heat reservoirs. We show that the first-order material equation of the state leads thermodynamic cycle shape keeping it closer to the optimum cycle. Conditions to improve the performance of the second-order materials are discussed. In addition, we infer key remarks for prototype design regarding the power density and efficiency reachable in different configurations.

Ferromagnetic L1 0 Phase Formation in the Mn–Al–C Alloys Induced by High-Pressure Spark Plasma Sintering

Structural and magnetic characterization of Mn–Al–C permanent magnets obtained by spark plasma sintering (SPS) is reported. The transformation from the parent <inline-formula> <tex-math notation=LaTeX>

A Multiscale Modeling of Magnetic Shape Memory Alloys: Application to NiMnGa Single Crystal

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Structural and magnetic properties of an anisotropic M-type LaCo-substituted strontium hexaferrite

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Enhanced magnetoelectric voltage in ferrite/PZT/ferrite composite for AC current sensor application

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Spark Plasma Sintering Co-Sintered Monolithic Transformers for Power Electronics

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Study of the first paramagnetic to ferromagnetic transition in as prepared samples of Mn-Fe-P-Si magnetocaloric compounds prepared by different synthesis routes

This paper presents a new multiscale modeling dedicated to magnetic shape memory alloys. It involves four scales from the domain scale to the macroscale. The model is presented, and the simulation results are compared with experiments carried out on a NiMnGa single crystal.

Effect of non-magnetic and magnetic trivalent ion substitutions on BaM-ferrite properties synthesized by hydrothermal method

Rare-earth-free permanent magnets returned to the forefront of scientific and technological concerns about the environmental and economical issues. The emergence of new markets, control of costs and availability of raw materials encourage to look for alternative materials containing much less, or no, rare earth elements selected from the most common and most available. The hexaferrite doped with lanthanum and cobalt present interesting properties to succeed the rare-earth magnets. The structural and magnetic properties of a strontium hexaferrite are presented in this paper, and two models are developed in order to correlate structural and magnetic properties.