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91.
Samples of Fe100−xGax (x=8.3, 17.9, 20.5 and 23.3) were prepared by rapid solidification from the melt using a single Cu roller. X-ray diffraction studies of all samples showed them to be single phase with the disordered BCC structure. No evidence of superlattice reflections from D03 ordering was observed for any of the samples. Room-temperature 57Fe Mössbauer effect spectra indicated that all samples were ferromagnetically ordered. Spectra were fit to distributions of hyperfine fields. The x=8.3 sample showed a hyperfine field distribution that was single peaked and indicated a reasonably random distribution of local Fe environments. The x=17.9 and 20.5 samples showed hyperfine field distributions that were bimodal and indicated two distinct local Fe environments. The x=23.3 sample showed three distinct field components. It is suggested that the x=8.3, 17.9 and 20.5 alloys are primarily a disordered BCC phase. The x=8.3 alloy shows a small amount of short-range Ga–Ga pairing, while this short-range pairing is significantly greater in the x=17.9 and 20.5 alloys. The three field components in the x=23.3 alloy correspond well to the two sites associated with the D03 phase and a third component corresponding to a remaining L12 phase suggesting the presence of at least short-range D03 clustering in this alloy. 相似文献
92.
Dung-Shing Hung Chen S. Tsai Chin-Chung Yu Yung Liou Shang-Fan Lee Po-Chieh Chiang Chih-Sung Ho Yeong-Der Yao 《Journal of magnetism and magnetic materials》2006
In this study, Fe/Ag/Fe/Ag ferromagnetic structures were epitaxially grown on a GaAs(1 0 0) substrate. Using the Network Analyzer (Agilent 8510C), FMR (ferromagnetic resonant) signals were observed in samples as the in-plane magnetic field was applied to either hard- or easy-axes. Of interest was that our sample demonstrated a FMR-switching behavior in hard-axis but not in easy-axis. The detecting data showed that the switch magnetic field was much smaller than what has been stated previously in Fe/Cu/Fe systems by other laboratories. In addition to the frequency switch in FMR, we also observed a magnetic reversal behavior in its M–H curve. Data presented that both of the FMR and magnetic reverse took place in the same direction (hard-axis). 相似文献
93.
D. Coupier 《Journal of statistical physics》2006,123(2):473-495
A d-dimensional Ising model on a lattice torus is considered. As the size n of the lattice tends to infinity, a Poisson approximation is given for the distribution of the number of copies in the lattice of any given local configuration, provided the magnetic field a = a(n) tends to −∞ and the pair potential b remains fixed. Using the Stein-Chen method, a bound is given for the total variation error in the ferromagnetic case.
AMS SUBJECT CLASSIFICATION: 60F05, 82B20. 相似文献
94.
95.
C. Cammarota 《Journal of statistical physics》1991,63(3-4):783-790
The random variable number of cluster defined on the configurations of a ferromagnetic Ising model at zero field and inverse temperature on a graphG is considered. The Gibbs average at=0 is proved to be greater than the one at>0 if the degree ofG is not greater than 3. 相似文献
96.
Phase pure, coarse crystalline Bi2NaRuO6 was synthesized in a hydrothermal approach. It displays a new crystal structure (Pnma (62), a = 12.1408(1) Å, b = 7.49282(6) Å, c = 12.1163(1) Å, Z = 8), which is characterized by a quasi-1D poly-oxoanion composed of (RuO6) octahedra sharing oxygen atoms in trans position. The magnetic response at high temperatures is described by a Curie-Weiss law reflecting strong antiferromagnetic interactions. The obtained effective magnetic moment complies with the d3 configuration for Ru5+. Below 208 K a weakly ferromagnetic state evolves while no phase transition could be observed in a heat capacity measurement. The compound displays activated electrical conduction. The overall composition and the ionic radii ratios of the constituents encourage to apply elevated hydrostatic pressure in order to realize the title compound in a double perovskite type arrangement, instead of the chain-like structure encountered at ambient conditions. 相似文献
97.
Maghemite sub-micrometer-sized spheres were successfully prepared by a simple solvothermal reduction route at relatively low temperature. The as-obtained sample was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) measurements. XRD and XPS analyses indicate the formation of γ-Fe2O3 phase. TEM results reveal that the γ-Fe2O3 particles are spherical with the diameter of 200-400 nm. Magnetic measurements show that the Curie temperature of γ-Fe2O3 sub-microspheres is over 400 K and the sample exhibits ferromagnetic behavior at room temperature. It is found that the sub-microspheres possess high saturation magnetization of 81 emu/g at 300 K. 相似文献
98.
The synthesis, crystal structure and magnetic properties of the cyano-bridged complex [{Cu(cyclam)}3{Fe(CN)6}2] · 6H2O are reported. Its structure is made up of centrosymmetric S-shaped pentanuclear [{Cu(cyclam}3{Fe(CN)6)}2] units, in which three [Cu(cyclam)]2+ units are alternatively bridged by two trans-CN groups of [Fe(CN)6]3− anions and water molecules. The pentanuclear Fe2Cu3 units are held together by two complementary and very weak Fe–CN?Cu1 bonds, forming a rope-ladder chain along the c axis. The compound exhibits a ferromagnetic interaction between the Cu(II) and Fe(III) ions as a consequence of the orthogonality of their magnetic orbitals of σ and π nature, respectively. The magnetic data were fitted to the calculated magnetic susceptibility equation for a pentanuclear model, leading to the following magnetic parameters: J1 = 9.0(3) cm−1, J2 = 3.8(4) cm−1, g = 2.2, θ = −1.2 K. These results show that the interactions through the long Cu–N axial bonds are not so weak as is usually assumed. 相似文献
99.
Laser beam interaction with alloys belonging to the Ni-Mn-Ga ferromagnetic shape memory alloy group has been investigated in order to assess the possibilities to use laser radiation for processing these materials, as for machining, joining or surface modification. The brittleness of Ni-Mn-Ga alloys is, as expected, an important factor and the formation of cracks appears to be difficult to be avoided. The laser interaction leads to vaporization on the impact zone and the changes in the chemical composition have been analyzed with respect to the beam parameters for penetration and surface melting, respectively. 相似文献
100.
Renu Mahajan Himani Nandedkar Sheeba Daniel 《Molecular Crystals and Liquid Crystals》2013,570(1):697-707
Abstract The present work deals with synthesis of two homologous series possessing ester and amide linkage and a large lateral aryl substituent. The large lateral group is attached to the main molecule through an amide linkage. Mesogenic amides are rare even when the amide linkage is present in the main molecular framework. However, in the present work the compounds containing amide linkage in lateral moiety also exhibit mesophases of high thermal stability. 相似文献