Papers by Keyword: Magnetism

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Authors: Zong Lin Liu, Hong Kuan Yuan, Hong Chen
Abstract: The geometric, electronic, and magnetic properties of Ho-doped Sin (n=1-12, 16, and 18) clusters are studied via the density functional theory with the generalized gradient approximation. The results show that the Ho atom in the most stable HoSin clusters always occupies the surface site. Starting from n=18, the Ho atom abruptly drops into the center of Si frame, forming the Ho-encapsulated Si cages. The stabilities of HoSin clusters increase with increasing size n. The Ho atom in HoSin clusters enhances their chemical activities. Moreover, the magnetisms of HoSin clusters are independent of their geometric structures, and the Si and Ho atoms are antiferromagnetic.
Authors: Kevin E. Elkins, Girija S. Chaubey, Vikas Nandwana, J.Ping Liu
Abstract: Chemical reduction of ferric acetylacetonate (Fe(acac)3) and platinum acetylacetonate (Pt(acac)2) using polyol as a reducing agent as well as an effective surfactant, has successfully yielded monodisperse FePt nanoparticles with a size of approximately 2 nm. When annealed samples were compared to FePt nanoparticles synthesized using oleic acid and oleylamine as the surfactants under identical conditions, nearly 30% increase in coercivity (Hc) was achieved with the new, simple and economic method.
Authors: Hong Fang Zhang, Chee Leung Mak, Yu Wang, L.B. Kong, Helen Lai Wah Chan
Abstract: A new kind of multiferroic three-ply-structured nanoceramic composites consisting of nanosized alloy-based magnetostrictive (MS) and ferroelectric powders (FE) were fabricated successfully by a conventional solid state reaction in air or argon ambient in our previous investigation. But there are still some problems needed to be solved, for example, the magnetic aging and decrease of saturated magnetization phenomena occurred in samples are perhaps related to the harsh preparation conditions such as storage duration and sintering atmosphere and so forth. In this paper, we will review the characteristics of the novel nanocomposites by means of the microstructure and magnetism existed in the samples with nanosized MS powders (i.e. (Tb0.3Dy0.7)0.75Pr0.25Fe1.55, Sm0.88Nd0.12Fe1.93) as fillers. Also, we hope some reasonable explanations and deeper understandings can be concluded about the proposed ageing and magnetism reduction exhibited when the samples were subjected to co-firing in air or argon ambient. Finally, the potential improvement and multifunctional applications in the future are also suggested.
Authors: Xiu De Yang, Bo Wu, Song Zhang
Abstract: By using generalized gradient approximation (GGA) scheme within the density functional theory (DFT), the electronic and magnetic properties of Hg2CuTi-type Heusler alloy Ti2FeAl were investigated. The results reveal that a 100% spin polarization appears at Fermi level (εF) in Ti2FeAl, and is maintained during lattice range of 5.1Å~6.2Å. Ti2FeAl is one of stable Half-Metallic Ferromagnets (HMF) with a spin-minority gap of 0.5 eV at εF and total magnetic moment of 1μB per unit cell. Our studies also indicate that the competition between RKKY-type indirect exchange and direct hybridization of d-electronic atoms plays a dominating role in determining the magnetism.
Authors: L. Ressier, H. Jaffres, E. Snoeck, D. Bertrand, A.R. Fert, J.P. Peyrade, A. Schuhl, F. Nguyen van Dau
Authors: Ronald Gibala, W.A. Counts, C. Wolverton
Abstract: We have used density functional theory (DFT) to determine binding energies (BE’s) of carbon-vacancy (C-v) point-defect complexes of probable importance to C-based anelastic relaxation processes in fcc iron alloys. Calculations are presented for three types of stable point defect clusters: C-v pairs, di-C-v triplets, and tri-C-v quadruplets. We demonstrate semi-quantitative consistency of the calculated BE’s with internal friction results on Fe-36%Ni-C alloys. The BE’s, which are in the range-0.37 eV to-0.64 eV, were determined for a hypothetical non-magnetic (NM) fcc Fe. The effect of the magnetic state of fcc Fe on some of these quantities was investigated by DFT and is shown to be significant; the BE’s appear to be reduced in antiferromagnetic (AFM) fcc Fe.
Authors: D.A. Vinnik, S.A. Gudkova, R. Niewa
Abstract: Barium hexaferriteBaFe12O19single crystals hexagonal platelet shape and sizes of up to 8 mm were grown of lead oxide and sodium oxide based fluxes at 1260 °C. The unit cell parameters of single crystals grown using different fluxes is in good agreement with literature data. Substitution of Ba by Pb was detected, but with only negligible influence on unit cell parameters and Curie temperature.
Authors: Fernanda A. Sampaio da Silva, Daniel Rodrigues, Gilberto Vicente Concílio, Jose Adilson de Castro, Marcos Flavio de Campos
Abstract: B-H loop obtained from frequencies higher than 40 Hz can be satisfactorily adjusted by Superellipse model. Examples of application of the Superellipse model for sintered stainless steel 410 are presented. The parameters of model (four parameters) may have assigned physical meanings that reveal magnetic behavior, such as coercivity and remanence. Furthermore, they are directly related to the aesthetics of the B-H loop. The Superellipse model is very versatile, describing the most closed shapes (rods) and the more open (rectangular). The obtained parameter values reflect the magnetic variability of sample. In addition, by applying the model it was possible to analyze the magnetic and structural properties of a sintered stainless steel sample.
Authors: Hong Yan Zhang, Jun Wang, Shao Hua Fan
Abstract: In this paper, we report the synthesis of the bifunctional Fe3O4@SiO2@Eu-polyoxometalates particles. The magnetite nanoparticles (Fe3O4) homogeneously coated with silica spheres prepared with the Stöber method. The so-obtained Fe3O4@SiO2 core/shell particles were modified by 3-aminopropyltriethoxysilane and finally grafted with the luminescent Europium -polyoxometalates. The core-shell particles were characterized by scanning electron microscopy, transmission electron microscopy, FT-IR, UV, magnetism and luminescence spectroscopy. The results indicated that the core-shell particles show both interesting luminescence and magnetic properties.
Authors: Li Wei Qian, Xiao Ling Hu, Ping Guan, Xiao Qing Guo
Abstract: Novel Bi-Functional Magnetical Chiral Ionic Liquids (MCILs) Derived from Imidazolium and Pyridinium Were Synthesized via Simply Two Step Reactions. Optically Active Ionic Liquids Have an Asymmetric Carbon Atom Linked to the Positively Charged Imidazole Ring or Pyridine Ring, while the Magnetical Anion Contains Tetrachloroferrate (FeCl4-), their Properties of Chirality and Magnetism Were Characterized. the Structure of MCILs Would Promise a New Class of Bi-Functional Ionic Liquids.
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