Papers by Keyword: Magnetism

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Authors: S. D. Antipov, G. E. Gorunov, N. S. Perov, M. N. Pivkina, E. E. Said-Galiyev, A.S. Semisalova, P. N. Stetsenko
Abstract: The magnetic properties of small 4d, 5d metal nanoparticles of Pd, Pt (clusters) are attracting a great attention because these materials in bulk are paramagnetic. In this work we report the ferromagnetic-like behavior of the small Pt nanoparticles prepared by chemical method. Highly dispersed Pt clusters have been synthesized on the surfaces of a porous spherical γ-Al2O3 particles. The process of the chemical deposition of metalorganic fluid with employment of the supercritical fluid was used. The samples of the Pt/γ-Al2O3 nanoparticles have been prepared in INEOS RAS. The nanoparticles size distribution was determined by small-angle X-rays scattering (SAXS). It was found that the Pt clusters have a bimodal particle size distribution with two peaks: R1max=20 Å and R2max=40 Å. The magnetic properties of the clusters have been investigated, using VSM magnetometer, in magnetic field up to ±3 kOe and at a temperature range from 80 to 400 K. It was observed that Pt/γ-Al2O3 nanoparticles show the ferromagnetic-like behavior in whole specified temperature range, the value of coercivity decreases gradually from 130 Oe to 80 Oe. The origin of ferromagnetic-like behavior of the Pt/γ-Al2O3 nanoparticles is discussed.
443
Authors: Er Jun Kan, Ming Li
Abstract: Ordered spin structure in two-dimensional materials is critical to the use of such materials in spintronics. Here, based on first-principles calculations, we demonstrated the existence of magnetic homogeneity in integrated two-dimensional structures. Our calculations show that hydrogenated MoS2 can be magnetized with a ferromagnetic character. The doped electrons in 4d orbitals of Mo atoms through hydrogenation lead to strong exchange splitting, which is the mechanism behind the transition of magnetic states. Given the recent progress in chemical control of two-dimensional materials, our results open a new way to produce two-dimensional spintronics.
345
Authors: János Kodácsy
Abstract: Denomination Magnetism Aided Machining (MAM) comprises a number of relatively new industrial machining processes (mainly finishing and surface improving) developed presently, too. MAM is effective – among others – for polishing, deburring and burnishing of metal parts. The magnetic force makes these processes simpler and more productive. Machining force is generated by an adjustable electromagnetic field between two magnetic poles within the working area ensuring the necessary pressure and speed difference between the tools (abrasive grains, pellets or rollers) and the workpieces. The authors give a brief outline of these modern processes. The paper summarizes the results of the experimental research carried out by the authors mainly in the field of Magnetic Abrasive Polishing (MAP) and Magnetic Abrasive Barrel Deburring (MABD).
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Authors: Ming Ming Li, Pei Ji Wang, Chuan Guang Ding
Abstract: The electronic structures and magnetic properties of Pd-doped CdS have been studied by FLAPW method in the GGA. We find that the Pd-doped CdS becomes 100% spin polarized at fermi level when Pd substitutes for Cd atom both in 3×3×2 and 2×2×2 CdS supercells. The supercell magnetic moment reaches to 2.0μB. At the same time, the magnetic coupling interaction makes the occupied states more localized. The magnetism, the density of states, the spin density and band structure were studied as well.
198
Authors: D.A. Vinnik, S.A. Gudkova, R. Niewa
Abstract: Lead and aluminum substituted barium hexaferrite (Ba,Pb)Fe12–хAlхO19 single crystals were grown from lead oxide flux at 1260 °C as hexagonal plates with sizes of about 2 mm. A maximum substitution level of x = 4.82 was achieved for the first time for bulk single crystals. The variation of the unit cell parameters with Al content is in good agreement with literature data on exclusively Al substituted barium hexaferrite, while the substitution of Ba by Pb has hardly any influence. Similarly, Pb has only a negligible influence on the magnetic properties, while Al substitution significantly reduces the saturation magnetization in a very similar manner as known from Pb-free barium hexaferrite.
3
Authors: Alberto Ubaldini, V.P.S. Awana, S. Balamurugan, E. Takayama-Muromachi
Abstract: The ruthenocuprates family is a very interesting class of materials, because of the coexistence of superconductivity and magnetic ordering. Ruthenocuprates include RuSr2RECu2O8 and RuSr2(RE,Ce)2Cu2O10- (RE = rare earth elements or Y). It is possible to synthesize samples of these phases with Gd, Eu or Sm with normal synthesis conditions. For the others high-pressure high-temperature (HPHT) synthesis is required. We had successfully synthesized the RuSr2Tb1.5Ce0.5Cu2O10 by HPHT technique, starting from RuO2, SrO2, Tb4O7, CeO2, CuO and Cu. Around 300 mg of the mixture was allowed to react in a flat-belt-typehigh- pressure apparatus at 6GPa and 1200 °C – 1550 °C. The optimised temperature of synthesis was found to be in the range between 1350 °C – 1450 °C. The as-synthesized compound crystallized with a structure belonging to the space group I4/mmm. DC magnetic susceptibility versus temperature plot for RuSr2Tb1.5Ce0.5Cu2O10 in an applied field of 10 Oe demonstrated magnetic transition at 150 K but the superconducting transition was not clearly observed. To our knowledge this is the first successful synthesis of the Tb based Ru-1222 phase.
31
Authors: Dominik Legut, Mojmír Šob
Abstract: The ideal tensile strength along the [111] direction in the Fe3Al and Ni3Al intermetallic compounds with the D03 structure has been calculated from the first principles using the fullpotential linearized augmented plane-wave method (FP LAPW) within the density functional theory (DFT). The strains corresponding to the maximum sustainable stresses in both materials were determined and compared. The behavior of atomic magnetic moments as a function of strain was analyzed. The tensile test simulations have been theoretically simulated employing both the local density approximation (LDA) and generalized gradient approximation (GGA) for the exchangecorrelation potential.
77
Authors: Valentin Yu. Irkhin
Abstract: A review of fundamental works by Shubin and Vonsovsky on the formulation of the polar and s–d(f) exchange models is given. Their ideas are compared with subsequent developments in the theory of magnetism in d- and f-metals and their compounds. Modern approaches including various slave-boson and slave-fermion representations, formation of exotic quasiparticles etc. are discussed. Internal connections between different many-electron models (the Heisenberg, Hubbard, t–J, Anderson Hamiltonians) are presented. Description of anomalous rare-earth and actinide compounds (Kondo lattices, systems with heavy fermions and non-Fermi-liquid behavior) within the framework of the s–d(f) exchange model and related models is considered.
3
Authors: Akikazu Matsumoto, Naoyuki Kanetake
Abstract: The spheroidal graphite cast iron is widely used as a structural material in an industrial field. Possibility to be able to use by improving magnetic characteristic of spheroidal graphite as magnetic circuit material of product related to electromagnetism besides structure material. In this study, the influence that the amount of graphite precipitation , the matrix organization, and the structure gave to a magnetic characteristic was investigated in the spheroidal graphite cast iron that makes matrix ferrite by compounding C element and the Si element and heat-treatment. The graphite was completely precipitated at the heat-treatment temperature of 1173K or more, the organizatiom became a ferrite, and permeability rose. Moreover, Rough making by heat-treatment the size about the particle size of the ferrite and the appearance of the Fe-Si phase have raised permeability.
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Authors: Jin Chen, Hai Yan Zhang
Abstract: Magnetism Carbon coated iron nanoparticles were produced by DC carbon discharge method .The structure , size distribution , phase composition and magnetic properties of the particles were investigated using TEM , XRD and VSM. The result s show that the core of t he particles is iron , and the shell of the particles is onion shaped carbon. The hysteresis curves of the particles show acharacteristic of superparamagnetic material.
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