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The Sm2(Fe1−xMnx)14B (0 ≤ x ≤ 0.3) rare earth alloy was prepared by a reduction-diffusion method, and a corresponding reduction-diffusion model was established. The crystal structure, microscopic morphology, and magnetic properties were systematically characterized to investigate the effect of Mn doping. The results show that the diffusion of Sm into FeB proceeded with the formation of the Sm2Fe14B phase from the very beginning of the reaction. Sm2(Fe1−xMnx)14B alloy undergoes a transition from the ferromagnetic phase (x = 0) to the paramagnetic phase (x = 0.2), and the average magnetic moment of Fe decreases from 2.066 to 0.719 µB as observed by 57Fe Mössbauer spectroscopy. In addition, the Curie temperature decreases rapidly from 620 to 230 K. In other words, a wide temperature-regulation of TC can be achieved by adjusting the Mn content, which is attributed to the fact that Mn doping greatly weakens the atomic exchange interactions. These results provide value for potential applications of Re–Fe-based alloys in room temperature magnetic refrigeration.

An easy-plane FeSi3.5 composite with excellent magnetic properties and loss properties at MHz were proposed. The easy-plane FeSi3.5 composite has ultra-low loss at 10 MHz and 4 mT, about 372.88 kW/m3. In order to explore the reason that the Pcv of easy-plane FeSi3.5 composite is ultra-low, a none easy-plane FeSi3.5 composite, without easy-plane processing as a control group, measured the microstructure, and the magnetic and loss properties. We first found that the real reason why magnetic materials do not work properly at MHz due to overheat is dramatical increase of the excess loss and the easy-plane composite can greatly re-duce the excess loss by loss measurement and separation. The total loss of none easy-plane FeSi3.5 composite is much higher than that of easy-plane FeSi3.5 composite, where the excess loss is a major part in the total loss and even over 80% in the none easy-plane FeSi3.5 composite. The easy-plane FeSi3.5 composite can greatly reduce the total loss compared to the none easy-plane FeSi3.5 composite, from 2785.8 kW/m3 to 500.42 kW/m3 (3 MHz, 8 mT), with the main reduction being the excess loss, from 2435.2 kW/m3 to 204.93 kW/m3 (3 MHz, 8 mT), reduced by 91.58%. Furthermore, the easy-plane FeSi3.5 composite also has excellent magnetic properties, high permeability and ferromagnetic resonance frequencies. This makes the easy-plane FeSi3.5 composite become an excellent soft magnetic composite and it is possible for magnetic devices to operate properly at higher frequencies, especially at the MHz band and above.

Intelligent machines are knowledge systems with unique knowledge structure and function. In this paper, we discuss issues including the characteristics and forms of machine knowledge, the relationship between knowledge and human cognition, and the approach to acquire machine knowledge. These issues are of great significance to the development of artificial intelligence.

In this work, the composition dependence of high-frequency magnetic properties for the oriented hcp-Co1-xIrx soft magnetic films with negative uniaxial magnetocrystalline anisotropy (Kugrain) and in-plane uniaxial anisotropy field (Hu) is investigated. Both the saturation magnetization (Ms), Kugrain, and Hu are greatly affected by the composition of Ir. The (μi - 1) . fr of Co1-xIrx (with negative Kugrain) is larger than Acher's limit (without Kugrain) when x exceeds 0.14. The increasing percent of (μi - 1) . fr could get a maximum of 42% when x is 0.2. [ABSTRACT FROM AUTHOR]

A map displaying the matching characteristics and absorption performance for the metallic carbonyl iron composite in microwave frequency band is developed based on the origin of absorption peaks. In this map, the dependence of matching frequency fm on absorber thickness, input impendence, and absorption peak value is achieved simultaneously from the complex permeability and permittivity spectra without any approximation. From this map, the perfect matching frequency fpm and perfect matching thickness tpm at input impendence Z=1 can be directly searched. Moreover, the required absorber thickness and the reflection loss value at any expected frequency where the absorption peak locates can be directly observed. [ABSTRACT FROM AUTHOR]

Surface-modified planar-anisotropy Fe50Ni50 particle-resin composites have been studied in the microwave frequency range. After surface modification, the eddy current effect is suppressed effectively while the permeability is almost unchanged. High permeability and appropriate permittivity are obtained at the meantime. Simulated microwave reflection result shows that the matching thickness, corresponding frequency, μ and [variant_greek_epsilon] is coincident with the quarter wavelength matching condition. The surface-modified Fe50Ni50/resin composites can be attractive candidates for thinner microwave absorbers in L-band (1-2 GHz). [ABSTRACT FROM AUTHOR]

The effective permeability of flake-shaped FeCuNbSiB particles/nonmagnetic matrix composition in high frequency was measured and calculated. In contrast to the relatively larger size and irregular shape particles, the flake particles have higher permeability. The results are attributed to the different magnetic loss mechanisms. According to the skin-effect criterion, we find that the magnetic loss in flake particles is mainly caused by the natural resonance, compared with the eddy current effect in the larger size and irregular shape particles. Using the shape anisotropy, the flake soft magnetic particles overcome the difficulty of the relatively small intrinsic anisotropies and increase the natural resonant frequencies to the gigahertz range, leading to the higher real part and imaginary part of the permeability. The resonance peak of flake particles was simulated using the combination of the Landau–Lifshitz–Gilbert equation and Bruggeman’s effective medium theory considering a random spatial distribution of magnetic easy axes. Our theory simulation agrees well with the experimental data. [ABSTRACT FROM AUTHOR]

Several studies are conducted to explain the different microwave reflection characteristics exhibited by the surface-modified [Fe.sub.50][Ni.sub.50] fine particle composites. These composites are found to be extremely beneficial as the thinner microwave absorbers.

The complex permeability of the flake-shaped FeCuNbSiB composites fabricated by ball milling the annealed ribbons was measured in the frequency range of 0.1-18 GHz. The calculated results for higher permeability oriented composite and unoriented composite particles confirmed with the experimental data.

A chemical reducing method was used to prepare multiwalled carbon nanotubes filled with face centered cubic Co nanoparticles (MWCNTs/Co). The measurement of the relative permeability and permittivity spectra of MWCNTs/Co resin composites with 50 wt % powders indicated that the peak with minimum reflection loss (RL) value moved to lower frequencies and the RL value increased from 4.2 to 10.1 dB with the increase of the absorber's thickness from 2 to 6 mm.

The mechanical and magnetic properties of the compound of a single [Fe.sub.3]C cluster and single walled carbon nanotubes (SWNT) under uniaxial stress are studied by using first-principles study. The external tensile strain has induced a magnetic phase transition in the [Fe.sub.3]C-SWNT and the results have shown that the strong Fe-SWNT interaction has played a vital role in determining the magnetic properties of the compounds.

Microwave absorber using hierarchically branched Ni nanowires based composite is described. The resonance absorption character is discussed by fitting the permeability spectrum by using Landau-Lifshitz-Gilbert equation and Kittel formula.

First-principles calculations are used for studying the structures and magnetic and electronic properties of [Fe.sub.3]C cluster confined in various single-walled carbon nanotubes (SWCNT). The whole SWCNT + [Fe.sub.3]C system has exhibited a high spin polarization and has a potential use as spintronics devices with controllable structure and properties.

Presents an experiment which investigated the mechanism of diffusion of nitrogen atoms in crystal structure compounds. Indepth look at the methodology of the experiment; Details on the results.

Studies the interstitial nitrogen atom effects in NdFe10.5V1.5Nx compounds using magnetic and 57Fe Mossbauer spectra measurements. Influence of nitrogenation on these compounds; Examination of the magneto-volume effect and the chemical bonding effect of nitrogen atoms; Experimental procedures used in this study; Results of this study.

Materials consisting of nanometer-sized magnetic particles are currently the subject of intensive research activities. Especially, much attention has been paid to their promising features for microwave magnetic properties. Well dispersed Fe3O4 nanoparticles of 30 nm have been synthesized by oxidization method with NaNO2, and the microwave magnetic properties of the composites have been studied. The real and imaginary part of relative permittivity remained low and nearly constant in the region of 0.1–18 GHz, respectively. As a result, the resin composites having a thickness of 2.0–3.2 mm, and containing 20 vol% Fe3O4 in the form of nanoparticles with an average diameter of 30 nm, exhibited excellent electromagnetic wave absorption properties in the frequency range of 4.5–12.0 GHz. [ABSTRACT FROM AUTHOR]

Abstract  Magnetite (Fe3O4) nanoparticles were synthesized by chemical precipitation. To reduce the aggregation of Fe3O4 nanoparticles, an effective surface modification method was proposed by grafting polystyrene onto the Fe3O4 particles. The results of Fourier transform infrared spectra and elemental analysis showed that the polymer chains have been successfully grafted from the surface of the Fe3O4 nanoparticles and that the percentage of grafting can reach 73%. Transmission electron microscope showed that grafted polymer chains on nanoparticles could prevent the aggregation of Fe3O4 nanoparticles markedly in toluene and improve their compatibility with organic phase. Another finding was the grafting reaction did not alter the crystalline structure of the Fe3O4 nanoparticles according to the X-ray diffraction patterns, and the saturation magnetization of PS-Fe3O4 nanoparticles was found to be lower than bulk magnetite. [ABSTRACT FROM AUTHOR]

Aligned NiFe2O4 polycrystalline nanotubes have been successfully fabricated inside the nanochannels of porous anodic aluminum oxide (AAO) templates by wetting chemical deposition. A mixture of Fe nitrate and Ni nitrate, which was thermally decomposed at no less than 400 °C, was used to yield NiFe2O4 tubes. By varying the deposition conditions and the parameters of the templates, we could tailor the lengths and the outer as well as the inner diameters of the tubes. Transmission electron microscopy (TEM) images reveal that the nanotubes are uniform and well isolated. X-ray diffraction (XRD) and selected area electron diffraction (SAED) demonstrate that the as-obtained nanotubes can be indexed to polycrystalline cubic spinel. The Mössbauer spectra show that the magnetic hyperfine field is reduced with the decrease of the metrical temperature as well as the decrease of the size of nanoparticles. [ABSTRACT FROM AUTHOR]

Excellent soft magnetic properties have been achieved in a wide metal volume fraction (x) range for as-deposited (Fe65Co35)x(SiO2)1?xgranular films fabricated by magnetron sputtering. With the decrease in xfrom 0.7 to 0.5, the films exhibit small coercivity Hcnot exceeding 4?Oe and high electrical resistivity ? up to 5.48 × 103?µ??cm. A minimum Hcvalue of 1.7?Oe was obtained for the sample of x= 0.57 with ? = 2.86 × 103?µ??cm. At a frequency lower than 1.3?GHz, the real part ?' of complex permeability of this sample is about 170 and then decreases with frequency while the imaginary part ?? is visible when f> 1?GHz, which may be caused by anisotropy dispersion. The FMR frequency is as high as 2.4?GHz, implying a high cut-off frequency for high frequency applications. A study of high resolution transmission electronic microscope indicates that the samples consist of Fe65Co35particles uniformly embedded in an insulating SiO2matrix. The excellent soft magnetic property is ascribed to exchange coupling among magnetic particles. The investigation of the ?m-Hcurve evidences the existence of this inter-granule interaction. [ABSTRACT FROM AUTHOR]

The effect of IIIA metal and transition metal T substitution for Fe on crystal structure, magnetostriction and spontaneous magnetostriction, anisotropy and spin reorientation of a series of polycrystalline Tb0.3 Dy0.7 (Fe0.9 T 0.1)1.95 ( T=Mn, Fe, Co, B, Al, Ga) alloys at room temperature were investigated systematically. It was found that the primary phase of the Tb0.3 Dy0.7 (Fe0.9 T 0.1)1.95 alloys is the MgCu2-type cubic Laves phase structure for different substitution. The magnetostriction λ{ins} decrases greatly for the substitution of IIIA metal, B, Al and Ga, but is saturated more easily for Al and Ga substitution, showing that the Al and Ga substitution is beneficial to a decrease in the magnetocrystalline anisotropy of Tb0.3 Dy0.7 (Fe0.9 T 0.1)1.95 alloys. However, the substitution of transition metal Mn and Co decreases slightly the magnetostriction λ{ins}. It was also found that the effect of different substitutions on the spontaneous magnetostriction λ{in111} is distinct. The analysis of the Mössbauer spectra indicates that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry for Al and Ga substitution, namely spin reorientation, but it does not change evidently for B, Mn and Co substitution. [ABSTRACT FROM AUTHOR]

Mesoporous MnO2 nanowire array architecture exhibits enhanced capacitive and charge/discharge performance for electrochemical capacitors. [ABSTRACT FROM AUTHOR]

Presents a synthesis of a single phase gamma-Fe[sub 4]N type (Fe[sub 1] [sub x]Ni[sub x])[sub 4]N iron nitride compounds. Examination of the compounds by x-ray diffraction and Mossbauer spectroscopy; Reduction of lattice constants with increasing nickel content; Value of the average expansion of the unit cell for gamma-iron-nickel alloys.

Transmission line theory uses the complex nature of permeability and permittivity of a conventional magnetic absorber to evaluate its absorption properties and mechanism. However, because there is no method to obtain the electromagnetic parameters of a metamaterial-absorber integrated layer (composed of a medium layer and a periodic metal array), this theory is seldom used to study the absorption properties of the metamaterial absorber. We propose a symmetry model to achieve an equivalent complex permittivity and permeability model for the integrated layer, which can be combined with the transmission line theory to calculate metamaterial absorption properties. The calculation results derived from both the transmission line theory and the high-frequency structure simulator are in good agreement. This method will be beneficial in practical investigations of the absorption mechanism of a metamaterial absorber. [ABSTRACT FROM AUTHOR]

The oriented (P=B, Ni, and SiO2) soft magnetic films are prepared. Their morphology is measured using transmission electron microscopy (TEM), and reveals that these films exhibit good crystallinity and high degree of the c-axis orientation. The magnetic properties are thoroughly investigated as a function of doping x. Our results show that all of these films possess negative magnetocrystalline anisotropy as required by possible applications. Both the intrinsic and extrinsic contributions are considered to interpret the broadening of the ferromagnetic resonance spectral linewidth. The intrinsic Gilbert damping is identified as the main cause of the linewidth broadening, while the extrinsic part originating from inhomogeneities only plays a minor role. More interestingly, our results show that the damping constant can be controlled by using the doping method. [ABSTRACT FROM AUTHOR]

The microwave properties of spherical carbonyl iron particles with submicron- and micron-sizes are measured and calculated. In contrast to the micron size particles, the submicron size particles have higher permeability and better microwave absorbing performance in the low frequency band. According to the skin-effect criterion, the skin effect is a crucial mechanism in the micron and submicron size and it leads to a large damping factor. By using the Landau–Lifshitz–Gilbert equation and the theory of skin depth, we simulate the resonance peak of spherical particles with different sizes. Our theory simulation agrees well with the experimental data. [ABSTRACT FROM AUTHOR]

Fe-Co soft magnetic films with tunable high-frequency magnetic properties were successfully electrodeposited onto ITO conductive glass substrates. A significant shift of ferromagnetic resonance frequency fr from 1.1 to 4.2 GHz was manipulated by electrolyte temperature and an applied magnetic field. It is found that the in-plane uniaxial anisotropy field Hk is strongly affected by the electrolyte temperature and varies from 0 to 64 Oe by increasing the electrolyte temperature from 5 to 40 degC. The resonance frequencies calculated from the in-plane uniaxial anisotropy fields are not in agreement with those from experimental measurements. According to Hoffmann's ripple theory, an additional isotropic internal field Hadd is introduced to explain this discrepancy. [ABSTRACT FROM AUTHOR]

The relationship between spin, electron, and crystal structure has been one of the foremost issues in understanding the superconducting mechanism since the discovery of iron-based high-temperature superconductors. Here, we report Mössbauer and first-principles calculations studies of the parent compound SrFeAsF with the largest temperature gap (~50 K) between the structural and antiferromagnetic (AFM) transitions. Our results reveal that the structural transition has little effect on the electronic structure of the compound SrFeAsF while the development of the AFM order induces a redistribution of the charges near the Fermi level. [ABSTRACT FROM AUTHOR]