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Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe40Ni40B20 and Fe40Ni38Mo4B18 metallic glass ribbons. 90 MeV 127I beam was used for the irradiations. Irradiation doses were 5×1013 and 7.5×1013 ions/cm2. The relative intensity ratios D 23 of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy. 相似文献
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Kalinin SV Gorbachev DL Borisevich AY Tomashevitch KV Vertegel AA Markworth AJ Tretyakov YD 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(2):1189-1194
Computer simulations of the evolution of fractal aggregates in systems with conserved order parameter are described in this work. The aggregates are generated by diffusion-limited aggregation. This model describes such important processes as annealing of dendrite inclusions in solids, healing of cracks in ceramics, temperature-induced transformations in composites, relaxation of rough surfaces, aging of colloid particles, etc. It is shown that the evolution in fractal media differs significantly from that occurring in initially homogeneous systems and leads to different values of the scaling exponent. A relationship between the fractal dimension, mechanism of relaxation, and scaling exponent was also derived. 相似文献
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Amita Gupta Alexei Yu Ganin Parmanand Sharma Vikrant Agnihotri LM Belova KV Rao Mikhail E Kozlov AA Zakhidov RH Baughman 《Pramana》2002,58(5-6):1051-1059
We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show
a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are
found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there
exists no report in literature on any BiNi compound which is magnetic. 相似文献
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Using the recent results for the surface current density on cylindrical surfaces of arbitrary cross-section producing uniform
interior magnetic field we propose a method for obtaining solutions of Bean’s critical state model for general cylindrical
samples. The method uses the technique of conformal mapping to express the sample surface and the flux-fronts in terms of
a set of coefficients that depend on a parameter. The flux-fronts are to be determined by solving a system of nonlinear ordinary
differential equations for the coefficients. Retaining only a certain finite number of leading coefficients we get an approximate
solution. The procedure is illustrated by considering two cyclindrical samples — one with an elliptical cross-section and
the other with a non-elliptical cross-section. The virgin curve and small and large magnetization hysteresis loops for the
two samples are obtained. 相似文献
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We present a novel ac susceptibility technique for the study of vortex creep in superconducting thin films. With this technique
we study the dynamics of dilute vortices in c-axis oriented Y-123, Hg-1212, and Tl-1212 thin films, as well as a axis oriented Hg-1212 thin films. Results on the Hg-1212 and Tl-1212 thin films indicate that dislocation-mediated plastic
flux creep of single vortices dominates at low temperatures and fields. As the temperature (or the field) is increased, the
increasing vortex-vortex interactions promote a collective behavior, which can be characterized by elastic creep with a non-zero
μ exponent. Also, in some of these samples effects of thermally assisted quantum creep are visible up to 45 K in some of these
samples. In Y-123 thin films, creep is found to be collective down to the lowest temperatures and fields investigated, while
the quantum creep persists only up to 10–11 K. 相似文献
6.
Using recent results for the surface current density on cylindrical surfaces of arbitrary cross-section producing uniform
interior magnetic field and an assumed set of flux-fronts, solutions of Bean’s critical state model for cylindrical samples
with non-elliptic cross-section are presented. Magnetization hysteresis loops for two cross-sections with different aspect ratios are obtained.
A comparison with some exact results shows the limitations of this approach. 相似文献
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