Papers by Keyword: Magnetism

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Authors: Leyla E. Isaeva, D.I. Bazhanov, S.S. Kulkov, S.E. Kulkova, Igor A. Abrikosov
Abstract: In this paper we have studied from first-principles the effect of magnetism on the hydrogen-metal interaction and the binding properties of palladium with 3d-alloying atoms in the presence of vacancies induced during hydrogenation process. Our first-principles calculations were carried out by means of state of the art ab-initio method based on density functional theory and all-electron PAW-potentials. We have analyzed the changes of the atomic and electronic structures of palladium crystal induced by the presence of substitutional 3d-alloying atoms, interstitial hydrogen and structural defect (palladium vacancy). The obtained results have shown that magnetism can strongly affect the hydrogen-metal interaction in palladium based alloys. We have also demonstrated that the presence of vacancies in the palladium matrix can alter the interaction energy between hydrogen and alloying transition metal atoms.
Authors: Johan Moulin, Bhaskar Kaviraj, El Houcine Oubensaïd, Francisco Alves, Uday P. Deshpande, Ajay Gupta, Elisabeth Dufour-Gergam
Abstract: Thin films of amorphous FeCuSiNbB alloy have been deposited by RF sputtering with various deposition rates. The bulk oxygen content has been characterized using EDS and XPS. Its dependence on deposition rate shows that water vapour in the sputtering chamber is at the origin of the contamination. It allows also estimating the adsorption coefficient of the oxygen on the sample to be around 15 % at 350 K. The magnetic hardness and the resistivity increase with the contamination in oxygen. In devitrified films, this increase is also related to an enrichment of the residual amorphous matrix in oxygen.
Authors: Wen Zhi Li, De Xiang Fu, Yu Zhuang Liu, Yang Wang, Liang Xie, Yong Tao Li, Wei Chen, Li Xia Wang, Hong Guang Zhang
Abstract: The lattice structure and magnetism of polycrystalline CaMn7-xGaxO12 (x = 0, 0.1, 0.2, 0.3, 0.4) synthesized by solid state method have been investigated. The refined x-ray diffraction patterns show that a well single phase Ga doped CaMn7O12 crystals can be obtained by solid state method and their lattice structure is rhombohedral with R-3. The lattice parameter a linearly decreases while parameter c linearly increases with increasing doping concentration, leading to a lattice distortion. Magnetic susceptibility and inverse susceptibility as a function of temperature show that CaMn7-xGaxO12 and undoped CaMn7O12 behave the basically identical magnetic characterization, that is, there are two magnetic phase transitions at 90 K and 40 K. And the antiferromagnetic transitional temperature is not obviously influenced by non-magnetic Ga ions doping. However, the magnetization at temperature lower than 40 K is enhanced and there is a new transitional temperature point observed at temperature range between 40 and 90 K, which indicates that Ga ions participate into the magnetic interaction.
Authors: K.P. Hong, G. Goglio, Gérard Demazeau, D.-Y. Jung
Authors: Mihaela Popa, Guy Schmerber, Dana Toloman, Mihai S. Gabor, Amalia Mesaros, Traian Petrişor
Abstract: Undoped and holmium-doped ZnO thin films were obtained, using the sol-gel method. The films were characterized by scanning electron microscopy (SEM), Hall effect measurements, electron paramagnetic resonance (EPR) spectroscopy and superconducting quantum interference device vibrating sample magnetometry (SQUID-VSM). The Hall effect measurements have indicated a n-type conduction with a resistivity of about 3.2 Ω.cm for the undoped ZnO and of about 4.5 Ω.cm for the 5 at. % Ho-doped ZnO thin films. The EPR measurements have indicated the presence of interstitial zinc in the undoped ZnO and the presence of zinc vacancies in 5 at. % Ho-doped ZnO. Ho (5 at. %)-doped ZnO films exhibit superparamagnetism at 5 K, while a low paramagnetic behavior was observed at room temperature.
Authors: Qing Lin, Qing Mei Zhang, Guo Dong Tang, Yun He, Xue Hui Long
Abstract: The mixed valency character and antiferromagnetic coupling in molecule magnets materials NBu4MAII[FeIII(OX)3](MA=Co、Fe) were investigated by magnetic measurements and Mössbauer spectroscopy .In the sample NBu4CoII[FeIII(OX)3],the appearence of temperature point of spin-glass phase transition and magnetic phase transition under the zero-field-cooled AC magnetic measurements with the temperature range 5-100 K.The sample NBu4FeII[FeIII(OX)3] were carried out in the cooling modes in a field,and the sample exhibits multiple magnetic pole reversals in the warming mode magnetic measurements.The phenomenon of multiple magnetic pole reversals occurs in some of those ferrimagnetic materials consisting of magnetic anisotropy ions and two or more types of antiferromagnetically ordered magnetic ions.The compound NBu4FeII[FeIII(OX)3] contains two different spin carries; ie: Fe(II) (SFe(II) = 2), Fe(III) (SFe(III) = 5/2) comes from the Mössbauer studies.
Authors: János Kodácsy, János Liska
Abstract: Basically, the Magnetic Assisted (MA) processes of the surface finishing can be divided into two groups: processes based on abrasion and plastic deformation. In this paper the authors present the results of experimental and developing work regarding the Magnetic Assisted Roller Burnishing (MARB) process that operates by plastic deformation and the strain hardening effect. Using Finite Element Method (FEM) modelling software system was prepared to demonstrate the experimental results.
Authors: Sophie Guillemet-Fritsch, Christophe Tenailleau, Helene Bordeneuve, Abel Rousset
Abstract: Magnetic susceptibility measurements, magnetization and neutron diffraction results at low temperature for cobalt and manganese oxide spinel ceramics are presented. The Curie temperature varies similarly with the sample composition in ceramics and powders. The experimental molar Curie constant variation is explained by the presence of Co2+, CoIII, Mn3+ and Mn4+, and possibly Co3+ in the octahedral sites for the cobalt rich phases. The magnetic moments of the cations in tetrahedral and octahedral sites are not collinear and the global magnetization is oriented in a third direction.
Authors: Yasushi Endo, Yusuke Niimi, Ryoichi Nakatani, Yoshio Kawamura, Masahiko Yamamoto
Abstract: We have studied the magnetic properties of Co-Fe circular dot arrays with various thicknesses and diameters in order to determine the optimum thickness and diameter of these dot arrays with a single-domain state for the transmission of spin information. For the thickness of 10 nm, the magnetic state changes from a multi-domain state to a closure-domain state and further to a single-domain state with decreasing diameter. On the other hand, for the thickness of 30 nm and 50 nm, all magnetic states are in a vortex state, regardless of the diameter. From these results, it is found that the optimum thickness and diameter of Co-Fe circular dots with a single-domain state are, respectively, 10 nm and less than 100 nm.
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