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71.
The structure and magnetic phase transitions of the Gd2Fe17 compound are investigated by using a differential thermal/thermogravimetric analyzer, x-ray diffraction, and magnetization measurements. The result shows that there are two phase structures for the Gd2Fe17 compound: the hexagonal Th2Nilr-type structure at high temperatures (above 1243℃), and the rhombohedral Th2Zn17-type structure, respectively. A method to measure the magnetic moments of the Gd-sublattice and the Fe-sublattice in the Gd2Fe17 compound is presented. The moments of the Gd-sublattice and the Fe-sublattice in the Gd2Fe17 compound from 77 to 500 K are measured in this way with a vibrating sample magnetometer. A detailed discussion is presented.  相似文献   
72.
The possibility of phase separation in the substances with orbital ordering is analyzed. The additional charge carriers introduced due to doping favor the formation of nanosize inhomogeneities with the orbital structure different from that in the undoped material. The shapes and sizes of such inhomogeneities are determined.  相似文献   
73.
Optical and magneto-optical properties of three-dimensional magnetic photonic crystals, based on magnetite Fe3O4 embedded into an opal film matrix, are investigated in both transmission and reflection. A strong enhancement of the polar Kerr effect and a modification of the Faraday effect have been found near the photonic band-gap of about 1.8 eV. Unusual changes of hysteresis curves and their dependence on photon energy have been revealed in the spectral region where the magneto-optical effect reverses its sign. This phenomenon has been explained by two types of magnetite particles inside the opal matrix having different coercive fields and spectral behaviour.  相似文献   
74.
The rate of change of magnetizing field (field-slope), applied for the nondestructive method of magnetic adaptive testing, influences both signal-to-noise ratio and sensitivity of the chosen magnetic parameters with respect to the investigated degradation of the ferromagnetic material (degradation functions). Dependence of the degradation functions sensitivity on the field-slope is analyzed in this paper. It is shown that whereas sensitivity of the top-responsive degradation functions from around the top permeability of the nondegraded (reference) material drops down with increasing field-slope, sensitivity of the mild-responsive degradation functions from regions with lower permeability of the reference material is frequently field-slope-independent. The most favorable choice of the best degradation functions and of the proper magnetizing field-slope remains to be a question of optimum adaptation of the tests both to the investigated material and to the applied measuring technique.  相似文献   
75.
We investigate the dynamic hysteresis of nanoscale magnetic aggregates by employing Monte Carlo simulation, based on Ising model in non-integer dimensional space. The diffusion-limited aggregation (DLA) model with adjustable sticking probability is used to generate magnetic aggregates with different fractal dimension D. It is revealed that the exponential scaling law A(H0, ω)∼H0α·ωβ, where A is the hysteresis area, H0 and ω the amplitude and frequency of external magnetic field, applies to both the low-ω and high-ω regimes, while exponents α and β decrease with increasing D in the low-ω regime and keep invariant in the high-ω regime. A mean-field approach is developed to explain the simulated results.  相似文献   
76.
The paper is devoted to the establishment of experimental conditions, which ensure the repeatability of magnetic Barkhausen noise testing in practice. For this task, the measurements were performed on open flat samples using different experimental configurations, including: different magnetization frequencies, sampling rates, and filter cut-off frequencies; using a sample-wrapped coil and using attached pick-up coils of various dimensions, with different lift-offs of a single yoke magnet and of the attached coil. The sample magnetization was controlled by a vertical array of three Hall sensors; their readings were extrapolated to the sample surface to precisely define its field. After analysis of the results, a scheme for an optimized sensor with a controlled field waveform was suggested to improve the measurement repeatability. The important issues of signal processing and parameter applicability were also discussed in detail.  相似文献   
77.
Multiferroic ground states with a spatially modulated antiferromagnetic structure and electric polarization have been revealed in Eu1−xYxMnO3 (0.2?x?0.50.2?x?0.5) single crystals. While the slightly substituted (x?0.1x?0.1) compounds exhibited a transition from the incommensurate (IC) to the canted antiferromagnetic (CAF) state at TCA<TNTCA<TN, the transitions from IC to commensurate ferroelectric (C/FE) phase were observed at Tlock<TNTlock<TN for x>0.2x>0.2. Various phase transitions were observed in the magnetic fields up to 250 kOe along a, b, c axes by magnetization, magnetostriction and electric polarization measurements which show an existence of a spontaneous electric polarization below Tlock.  相似文献   
78.
Co1−xCrx   alloy nanowires with 0.01<x<0.930.01<x<0.93 were fabricated by electrodeposition in a porous alumina membrane from an electrolyte containing Co and Cr ions. The composition, structure and magnetic properties of the nanowires have been characterized. Cobalt-rich nanowires were electrodeposited at a potential of −1.0 V relative to Ag/AgCl and chromium-rich nanowires were deposited beyond −3.5 V. The optimized processing conditions include hydrogen annealing to give hysteresis loops for the Co80Cr20 nanowires with coercivity of up to 200 mT and squareness of up to 0.95. Magnetization of the Co80Cr20 nanowire is 77 A m2 kg−1 and the energy product of the arrays is 35 kJ m−3.  相似文献   
79.
80.
Comments on a recent article on an enhanced polarization mechanism for the metal cations modified amorphous TiO2 based electrorheological materials are presented, based upon an examination of the yield stress, which is a function of electric-field strength, of the materials. Using the deduced critical electric-field strengths, we find that the universal yield stress equation proposed collapses the data given by Qing Wu, Bin Yuan Zhao, Chen Fang, Ke Ao Hu, Eur. Phys. J. E 17, 63 (2005), onto a single curve.  相似文献   
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