High and Ultra-High Coercive Materials in Spring-Exchange Systems—Review, Simulations and Perspective

Chrobak, A.

doi:10.3390/ma15196506

Cited by 7 publications

(3 citation statements)

References 49 publications

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“…As is known, IMCs have unique magnetic properties-record coercivity values for bimetallic nanocrystals of 70-90 kOe and high values of saturation magnetization and Curie temperature [9][10][11][12][13]. Therefore, considerable efforts have been directed to obtain such systems (mainly FePt, CoPt) and to study their properties (such as particle morphology and magnetic characteristics), as can be found in the main studies during the last few years [14][15][16][17][18]. Although considerable progress has been made, the current level of achieved coercivity values remains far below predicted characteristics [17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Morphology and Phase Compositions of FePt and CoPt Nanoparticles Enriched with Noble Metal

Zakharov,

Popova,

Pugachev

et al. 2023

Materials

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The article reveals for the first time the features of nanoparticle morphology, phase compositions, and their changes when heating FePt and CoPt nanoalloys. Nanoparticles were obtained by co-reduction of precursor solution mixtures with hydrazine hydrate. The features were found by a complex of methods of X-ray diffraction (in situ XRD and X-ray scattering), TEM HR, and cyclic voltammetry. In addition, adsorbometry results were obtained, and the stability of different nanocluster structures was calculated by the molecular dynamics method. There were only FCC solid solutions in the X-ray patterns of the FePt and CoPt nanoalloys. According to XRD, in the case of nanoparticle synthesis with Fe and Co content less than 10 at. %, the composition of solid solutions was close to or practically equal to the composition of the as-synthesized nanoparticles quantified by inductively coupled plasma optical emission spectrometry. For systems synthesis with Fe and Co content greater than the above, the solubility limits (SLs) of Fe and Co in Pt were set 11.4 ± 0.7 at. % and 17.5 ± 0.6 at. %, respectively. Therefore, there were non-registered XRD extra-phases (XRNDPh-1) in the systems when CFe,Co ≥ SL. This statement was supported by the results of TEM HR and X-ray scattering: the smallest nanocrystals (1–2 nm) and amorphous particles were found, which qualitatively agreed with the sorbometry and SAXS results. Molecular dynamics calculations of stability for FePt and CoPt alloys claimed the structures of the most stable phase corresponded to phase diagrams (A1 and L12). Specific peculiarities of the morphology and compositions of the solid solutions of nanoalloys were established: structural blockiness (domain) and composition heterogeneity, namely, platinum enrichment of internal (deep) layers and homogenization of the nanoalloy compositions at relatively low temperatures (130–200 °C). The suggested model of the formation of nanoalloys during the synthesis, qualitatively, was compliant with the results of electrochemical deposition of FePt films on the surface of various electrodes. When nanocrystals of solid solutions (C(Fe, Co) < SL) were heated above specific temperatures, there were phase transformations with the formation of two-phase regions, with solid solutions enriched with platinum or iron (non-registered XRD phase XRNDPh-2). The newly formed phase was most likely intermetallic compounds, FePt3, CoPt3. As a result of the study, the model was developed, taking into account the nanoscale of the particles: XRDPh (A1, FeaPt1−a) → XRDPh (A1, Fem×a−xPtm−m×a+x) + XRNDPh-2 (Fen×a+yPtn−n×a−y) (here, m + n = 1, m ≤ 1, n ≤ 1).

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Section: Introductionmentioning

confidence: 99%

Morphology and Phase Compositions of FePt and CoPt Nanoparticles Enriched with Noble Metal

Zakharov,

Popova,

Pugachev

et al. 2023

Materials

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“…Soft magnetic nanoparticles (SMNs) represent an important field in materials science and engineering, since they exhibit unique and interesting characteristics that provide promising applications [ 1 ]. Typically, SMNs include ferrites, Fe–Ni, Fe–Si, Fe–Al, and Fe–Co based alloys, which have been studied intensively in recent years [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. Fe–Co nanoparticles show high saturation magnetization and Curie temperature values, allowing the development of numerous applications, such as hyperthermia magnetic treatment [ 2 ] or thermoablative cancer therapy [ 3 ], magnetic resonance imaging (MRI) contrast [ 4 , 5 ] (currently the most commonly used gadolinium diethylenetriaminepentaacetic acid - Gd–DTPA [ 6 ]), high-density data storage [ 1 , 7 ], advanced materials for microwave devices [ 8 ], exchange-spring permanent magnets [ 1 , 9 ], and new generation of magnetorheological fluids [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

Tailoring Magnetic Properties of Fe0.65Co0.35 Nanoparticles by Compositing with RE2O3 (RE = La, Nd, and Sm)

Djellal¹,

Pęczkowski

Mekki

et al. 2022

Materials

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Fe‒Co alloys are the most important soft magnetic materials, which are successfully used for a wide range of applications. In this work, the magnetic properties of lanthanide-substituted (Fe0.65Co0.35)0.95(RE2O3)0.05 (RE = La, Nd, and Sm) nanoparticles, prepared by mechanical alloying, are reported. Our comprehensive studies (X-ray diffraction, Mössbauer spectroscopy, scanning electron microscopy with X-ray energy dispersive spectrometry, SQUID magnetometry and differential scanning calorimetry) have revealed different properties, depending on the dopant type. The RE2O3 addition led to a decrease in the crystallite size and to an increase in the internal microstrain. Moreover, because of the high grain fragmentation tendency of RE2O3, the cold welding between Fe–Co ductile particles was minimized, indicating a significant decrease in the average particle size. The parent Fe0.65Co0.35 alloy is known for its soft ferromagnetism. For the La-substituted sample, the magnetic energy product was significantly lower (0.450 MG.Oe) than for the parent alloy (0.608 MG.Oe), and much higher for the Sm-substituted compound (0.710 MG.Oe). The processing route presented here, seems to be cost-effective for the large-scale production of soft magnetic materials.

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“…Они характеризуются высокими энергетическими показателями (cosφ ≈ 1, η = 0,85÷0,98), весьма значительной кратковременной перегрузочной способностью по моменту, достигающей 5-10-кратного . значения от номинального, высокими массогабаритными показателями [5,7,13].…”

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Analytical Calculation of Magnetoelectric Valve Motor and Definition Inductive Parameters of Its Windings

Afanasyev,

Genin,

Vasileva

et al. 2023

Vestn. Čuv. univ.

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To implement the dynamic properties of the designed valve motors and achieve the proper quality of transient processes in the drives of complex mechanisms, it is necessary to study their electromagnetic and functional characteristics with the calculation of the inductive parameters of the windings. The purpose of the study is to study the electromagnetic and functional characteristics of the magnetoelectric valve motor and determine the inductive parameters of its windings. Materials and methods. The magnetic field of the machine is divided into a set of horizontal stripes (mediums), analyzed independently of each other. It is assumed that the magnetic field in these stripes is plane-parallel, and at the boundaries of the selected stripes the conjugation conditions are met: scalar magnetic potentials and normal components of magnetic induction do not undergo a jump (discontinuity). The magnetomotive force of the stator winding, the coercive force of magnets and the magnetization of soft magnetic ferromagnetic media are considered as sources of the magnetic field. Expressions for describing scalar magnetic potentials and normal components of magnetic induction in selected bands are obtained using the Fourier variable separation method. Research results. A study of the electromagnetic and functional characteristics of the motor was carried out using a mathematical model of the magnetoelectric valve motor based on the Fourier method of separation of variables with the division of the active region into homogeneous sections in the form of magnetic sheets. The model enables to determine magnetic inductions for any coordinate points x, y of the active region of the motor magnetic system. Expressions describing the inductive parameters of the windings are obtained, and the equations of the state of the motor are given for the case when the currents in the phase windings of the stator are in antiphase with their no-load EMF. Conclusions. Mathematical models of valve motors, built on the basis of the Fourier variable separation method, make it possible to determine the electromagnetic characteristics of motors and the inductive parameters of windings necessary for calculating transient processes. The most effective is valve motor control, when the phase currents are in antiphase with the no-load EMF. In this mode, with the absence of longitudinal current and with a power factor close to unity, the equations of state of the motor are of the second order.

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High and Ultra-High Coercive Materials in Spring-Exchange Systems—Review, Simulations and Perspective

Cited by 7 publications

References 49 publications

Morphology and Phase Compositions of FePt and CoPt Nanoparticles Enriched with Noble Metal

Morphology and Phase Compositions of FePt and CoPt Nanoparticles Enriched with Noble Metal

Tailoring Magnetic Properties of Fe0.65Co0.35 Nanoparticles by Compositing with RE2O3 (RE = La, Nd, and Sm)

Analytical Calculation of Magnetoelectric Valve Motor and Definition Inductive Parameters of Its Windings

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