Residual Stresses VII, ICRS7
Magnesium - Science, Technology and Applications
Eco-Materials Processing & Design VI
Silicon Carbide and Related Materials 2004
Materials Structure & Micromechanics of Fracture
Cross-Disciplinary Applied Research in Materials Science and Technology
Materials Science, Testing and Informatics II
Advances in Materials Manufacturing Science and Technology
Recrystallization and Grain Growth
Explosion, Shock Wave and Hypervelocity Phenomena in Materials
High Temperature Corrosion and Protection of Materials 6
Silicon Carbide and Related Materials 2003
Paper Title Page
Abstract: Ferromagnetic oxides with ordered double-perovskites Sr2FeMoO6 and Sr2CrReO6 are known to be in a half-metallic ground state with high Curie temperatures Tc, and hence one of the promising materials for spin electronics. This paper reports epitaxial growth and micro-structural, magnetic, and electrical characterization of thin films of these oxides. It is shown that a coherent growth without strain relaxation, which is accomplished by the use of substrate or buffer layers with a small (0.1%) lattice match, is essential to obtain high quality films with both atomically flat surface and high magnetization values expected for their half-metallicity
Abstract: In this work the giant magnetoimpedance effect has been found in Fe89B4Hf7 nanocrystalline ribbons. There is an optimal annealing temperature about 650°C for obtaining a large magnetoimpedance. The magnetoimpedance can reach 208% for Fe89B4Hf7 annealed at 650°C for 20min. meanwhile, it has been found that the magnetoimpedance in FeHfB shows a good thermal- heating stability, which is useful for application.
Abstract: Using pulsed laser deposition we prepared Fex-C1-x films on Si (100) substrates. We show that the lightly Fe-doped amorphous carbon films on Si substrate have large MR at room temperature. At T=300K and B=5T a large positive MR of 138% was found in Fe0.011-C0.989 film. Furthermore, we find that when temperature T<258K, the MR of Fe0.011-C0.989 film on Si substrate is negative and when 258K
Abstract: NiFe(2nm)/Cu(tCu)/Co(1.5nm) sandwiches were deposited on Ta buffer layer by magnetron sputtering method. Small angle X-ray diffraction analysis was made to investigate the structural characterizations of the sandwiches. It has been obtained that MR value showed a maximum at tCu=2nm when Cu spacer thickness changed, which is contributed by the effect of shutting and interlayer coupling. The Cu layer was deposited at two different rates. Larger MR ratio was observed with a lower deposition rate. The result was discussed in terms of magnetic reversal fields. In addition, the sandwiches were subjected to field annealing at different annealing temperatures. MR ratio has exhibited a largest increase after annealing at 175oC with a magnetic field of 750Oe applied.
Abstract: Fe61Co39 nanoparticles were prepared by hydrogen plasma metal reaction. The as-synthesized nanoparticles were characterized by x-ray differaction (XRD), transimition electron microscope (TEM) and superconducting quantum interference device (SQUID). The nanoparticles are spherical in shape, have bcc structure with the mean particle diameter of 41 nm, and are basically ferromagnetic with a slight amount of superparamagnetic part. The saturation magnetization and coercivity of the nanoparticles at 4.2 K are 190.15 emu/g and 1280 Oe, respectively. The blocking temperature is 250 K in 100 Oe and decreases with increasing the magnetic field.
Abstract: FeCuNbSiB and FeZrBCu nanocrystalline ribbons can be obtained directly through the melt- spinning technique without additional annealing processes. The giant magnetoimpedance can be observed in FeCuNbSiB and FeZrBCu as quenched ribbons. The addition of Cu improves the nano-crystallization of a-Fe(Si) or a-Fe phase and reduces the grain size in FeCuNbSiB and FeZrBCu as quenched ribbons, which enhances the magnetoimpedance via increasing the variation of permeability under fields. The present experimental results reveal a novel route to fabricate the Fe based nanocrystalline soft magnetic materials with giant magnetoimpedance effect.
Abstract: Magnetoresistive switch effect (MRS effect) devices containing two gold (Au) electrodes with a gap less than 2 µm were successfully fabricated on semi-insulting GaAs substrates by wet etching method. Huge MRS effect was observed. Magnetoresistance (MR) ratio reached 1,000,000% under the magnetic filed of 1.5 T when the devices were operated just above the threshold voltage. The magnetic field sensitivity at small magnetic fields was significantly improved. MR ratio of more than 1000% was achieved at 0.03 T. A relative high MR ratio of 100,000% under the magnetic filed of 1.5 T was also achieved when the devices operating before the threshold voltage.
Abstract: The layered manganese oxides LaSr2Mn2-xTxO7 (T=Fe, Cr and Ni) has been prepared. The effect of substitution of transition metal ions for Mn on magnetic and magtoresistance properties has been studied. The compound has a tetragonal symmetry and the lattice parameters a decreases with increasing the doped content but the parameter c increases with x. It indicates that the MnO6 octahedron increase the distortion with x content. With the x increase, their ferromagnetic property was depressed. The Neel temperature TN was depressed gradually from 138K to 89K, 95K and 85K at x=0.3 for T=Fe, Ni and Cr respectively. Their magnetoresistance MR is gradually enhanced for all doped system. It suggests that the introduce of disorder in B-site have an important effect on the magnetic exchange and magnetoresistance because of the weaken of the double-exchange (DE) interaction.
Abstract: Exchange-bias (Hex) of NiFe/NiO bilayers grown epitaxially on MgO(100) and MgO(111) have been measured in order to understand exchange biasing phenomena more clearly. According to HRXRD, the separate reflections of MgO and NiO were observed, which implied that NiO layers grew epitaxially on MgO substrates. The rms roughness (Rrms) of NiO on MgO(100) measured by AFM was 1.79 Å while that of NiO on MgO(111) was 17.85 Å. Despite a higher Rrms, the value of Hex, 85 Oe in the case of NiFe/NiO on MgO(111) was larger than that of NiFe/NiO on MgO(100), 47 Oe, probably due to stronger effect of (111) texture of NiO surface. But low Hex of NiFe/NiO on MgO(111) implied that exchange biasing was generated by not only upcompensated spins but also compensated spins of NiO. Hex of NiFe/NiO bilayer grown on Si(100) was 118 Oe. According to SEM, grain size of NiO surface grown on Si(100) was very small, which mean its domain size was also very small. The explanation of the effect of domain size was consistent with random field model.
Abstract: The characteristics of microstructures, martensitic transition, and magnetic field- induced strains of melt-spun ribbons are reviewed. The preferential alignment of crystal grains in the spun ribbons depends not only on the composition, but also on the spinning velocity. The increase of spinning velocity decreases the temperature of martensitic transition and decreases the enthalpy change. The anisotropies and retardance of field-induced strains was discussed, especially for the influence of the texture and annealing of the ribbons.