Optimum thickness of soft magnetic phase in FePt/FeCo permanent magnet superlattices with high energy product and large magnetic anisotropy energy
TL;DR: In this article, the B2 type FeCo layers become anisotropic with varying interlayer spacing and enhanced magnetic moments, resulting in high maximum energy product for (FePt)4/(FeCo)8 which is nearly double the calculated value for bulk FePt. The calculation of the magnetic anisotropy energy shows that the optimal thickness of the soft magnetic phase for good permanent magnet behaviour of the superlattice is less than ∼2 nm.
Abstract: Ab initio calculations on hard/soft (FePt)m/(FeCo)n, (m = 4, 6, 8 and n = 2-2m) magnetic superlattices show that the B2 type FeCo layers become anisotropic with varying interlayer spacing and enhanced magnetic moments. The average magnetic moment in superlattices is higher than in bulk FePt, resulting in high maximum energy product for (FePt)4/(FeCo)8 which is nearly double the calculated value for bulk FePt. The calculation of the magnetic anisotropy energy shows that the optimal thickness of the soft magnetic phase for good permanent magnet behaviour of the superlattice is less than ∼2 nm.
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TL;DR: In this article, the authors modified the Brillouin function to model the wasp-waisted magnetic hysteresis loop for soft-magnetic NiCoP-coated hardmagnetic M-type ferrite BaFe12O19 polystyrene (PS) bilayer composite film taking into account the effective applied magnetic field due to localized impurity phases.
Abstract: Brillouin function was modified to model the wasp-waisted magnetic hysteresis loop for soft-magnetic NiCoP-coated hard-magnetic M-type ferrite BaFe12O19 polystyrene (PS) bilayer composite film taking into account the effective applied magnetic field due to localized impurity phases and significant change in the azimuthal angle of the magnetic moment due to the formation of bilayer structure of film by the addition of PS. It is shown that there is a good fit to the experimental data observed in wasp-waisted magnetic hysteresis loop. The analysis shows that the forward magnetization and reversal process are typical.
22 citations
TL;DR: In this article, the effects of molding pressure, annealing temperature, and content of insulation on the magnetic properties of soft magnetic composites have been studied, where NiZn ferrites were selected as coating agents to improve the soft magnetic properties.
Abstract: NiZn ferrites were selected as coating agents to prepare NiZn/FeSiAl soft magnetic composites (SMCs) in order to improve the soft magnetic property. It is based upon the higher permeability of magnetic NiZn ferrites than that of traditional nonmagnetic coatings, and also relative higher resistance than that of MnZn ferrites. The effects of molding pressure, annealing temperature, and content of insulation on the magnetic properties were studied. As molding pressure increases, the effective permeability increases firstly and then decreases, while the core loss shows a reverse trend, and both get the best performance at 1.6 GPa. With increasing temperature, the permeability increases, reaches the maximum value at 660 °C and then decreases, while the core loss has a reverse trend, and both get the minimum value at 700 °C. The permeability increases with increasing NiZn from 0.1% to 3%, and then decreases. The D-C bias property of FeSiAl SMCs increases with increasing both mica and NiZn content. The larger resistance of mica also causes the better D-C bias property.
14 citations
TL;DR: In this article, the authors focus on the typical case of Co clusters embedded in various matrices to study interface magnetic anisotropy and magnetic interactions as a function of volume concentrations, and illustrate size-related and nanoalloy phenomena on magnetic properties in well-defined mass-selected clusters.
Abstract: In the frame of the 20th Anniversary of the Journal of Nanoparticle Research (JNR), our aim is to start from the historical context 20 years ago and to give some recent results and perspectives concerning nanomagnets prepared from clusters preformed in the gas phase using the low-energy cluster beam deposition (LECBD) technique. In this paper, we focus our attention on the typical case of Co clusters embedded in various matrices to study interface magnetic anisotropy and magnetic interactions as a function of volume concentrations, and on still current and perspectives through two examples of binary metallic 3d-5d TM (namely CoPt and FeAu) cluster assemblies to illustrate size-related and nanoalloy phenomena on magnetic properties in well-defined mass-selected clusters. The structural and magnetic properties of these cluster assemblies were investigated using various experimental techniques that include high-resolution transmission electron microscopy (HRTEM), superconducting quantum interference device (SQUID) magnetometry, and synchrotron techniques such as extended X-ray absorption fine structure (EXAFS) and X-ray magnetic circular dichroism (XMCD). Depending on the chemical nature of both NPs and matrix, we observe different magnetic responses compared to their bulk counterparts. In particular, we show how finite size effects (size reduction) enhance their magnetic moment and how specific relaxation in nanoalloys can impact their magnetic anisotropy.
14 citations
Cites background from "Optimum thickness of soft magnetic ..."
...Theoretical models on hard-soft permanent-magnet nanocomposites, predict superior performances than the current permanent magnets (Skomski et al. 2014)....
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...Theoretical models on hard-soft permanent-magnet nanocomposites predict superior performances than the current permanent magnets (Skomski et al. 2014)....
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9 citations
Journal Article•
TL;DR: In this paper, the local spin density approximation with first-principles full-potential linear muffin-tin orbital calculations including orbital polarization (OP) correction is presented. And the magnetic anisotropy is studied.
Abstract: The computational framework of this study is based on the local-spin-density approximation with first-principles full-potential linear muffin-tin orbital calculations including orbital polarization (OP) correction. We have studied the magnetic anisotropy
4 citations
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TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif
146,533 citations
TL;DR: An efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set is presented and the application of Pulay's DIIS method to the iterative diagonalization of large matrices will be discussed.
Abstract: We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.
81,985 citations
TL;DR: In this article, a method for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector is given, where the integration can be over the entire zone or over specified portions thereof.
Abstract: A method is given for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector. The integration can be over the entire Brillouin zone or over specified portions thereof. This method also has applications in spectral and density-of-state calculations. The relationships to the Chadi-Cohen and Gilat-Raubenheimer methods are indicated.
51,059 citations
TL;DR: In this paper, a new compound composed of Nd, Fe, and a small quantity of B (about 1 wt. %) has been found, which has a tetragonal structure with lattice constants a=0.880 nm and c=1.221 nm.
Abstract: A new compound composed of Nd, Fe, and a small quantity of B (about 1 wt. %) has been found, which has a tetragonal structure with lattice constants a=0.880 nm and c=1.221 nm. This phase, which has the approximate composition, 12 at. % Nd, 6 at. % B and balance Fe, possesses remarkable magnetic properties. From the approach to saturation an anisotroy constant of about 3.5 MJ/m3 can be calculated, while saturation magnetization amounts to 1.35 T. The magnetization versus temperature curve shows a Curie temperature of 585 K, which is much higher than those of the Fe and light rare earth binary compounds. Based on the new compound, sintered permanent magnets have been developed which have a record high energy product. Permanent magnet properties and physical properties of a typical specimen which has the composition Nd15B8Fe77 are as follows: Br =1.23 T, HcB =880 kA/m, HcI =960 kA/m, (BH)max =290 kJ/m3, temperature coefficient of Br =−1260 ppm/K, density=7.4 Mg/m3, specific resistivity=1.4 μΩm, Vickers hardn...
2,525 citations
TL;DR: Considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed and their potential impact on energy efficiency is discussed.
Abstract: A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy effi ciency in the total energy lifecycle, has accelerated research into energy-related technologies. Due to their ubiquity, magnetic materials play an important role in improving the effi ciency and performance of devices in electric power generation, conditioning, conversion, transportation, and other energy-use sectors of the economy. This review focuses on the state-of-the-art hard and soft magnets and magnetocaloric materials, with an emphasis on their optimization for energy applications. Specifi cally, the impact of hard magnets on electric motor and transportation technologies, of soft magnetic materials on electricity generation and conversion technologies, and of magnetocaloric materials for refrigeration technologies, are discussed. The synthesis, characterization, and property evaluation of the materials, with an emphasis on structure‐property relationships, are discussed in the context of their respective markets, as well as their potential impact on energy effi ciency. Finally, considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed.
2,465 citations