Ferromagnetic properties of Fe-substituted ZnO-based magnetic semiconductor

The diluted magnetic semiconductor Zn_1−x⁵⁷Fe_xO (x=0.01, 0.02, 0.03) compounds were prepared by the solid-state reaction method. The crystal structure of _Zn0.97⁵⁷_Fe0.03O${\mathrm{Zn}}_{0.97}{}^{57}{\mathrm{Fe}}_{0.03}\mathrm{O}$ at room temperature is determined to be a hexagonal structure of P6₃mc with lattice constants a₀=3.252 Å and c₀=5.205 Å by Rietveld refinement. The Bragg factors R_B and R_F were determined as 3.23% and 2.81%. From the inverse susceptibility versus T curve, the paramagnetic Curie temperature is found to be 2.7 K and effective moment is found to be 4.01 μ_B, thereby suggesting that the exchange interactions between Fe ions are ferromagnetic. Mössbauer spectra of _Zn0.97⁵⁷_Fe0.03O${\mathrm{Zn}}_{0.97}{}^{57}{\mathrm{Fe}}_{0.03}\mathrm{O}$ have been taken at various temperatures ranging from 4.2 to 295 K. Mössbauer spectrum for _Zn0.97⁵⁷_Fe0.03O${\mathrm{Zn}}_{0.97}{}^{57}{\mathrm{Fe}}_{0.03}\mathrm{O}$ at 4.2 K has shown ferromagnetic phase (sextet), and the spectra were fitted based on a random distribution model of Fe ions.     

Wavelet frame based surface reconstruction from unorganized points

Applications of wavelet frames to image restoration problems (e.g. image deblurring and inpainting) have been successful due to their redundancy and capability of sparsely approximating piecewise smooth functions like images (see e.g. ,  and ). However, wavelet frames have not yet been used for surface reconstruction problems. Recently in [6], connections between one of the wavelet frame based image restoration model ,  and  and variational models (e.g. the ROF model [45]) were rigorously established. Such connections not only grant new insights to wavelet frame based image restorations, it also case a geometric explanation to wavelet frame based approaches. This leads us to a wavelet frame based model, as well as a fast algorithm, to reconstruct implicit surfaces from unorganized point sets in R³${\mathbb{R}}^3$. We will demonstrate the effectiveness of the proposed model using several commonly used examples.     

Magnetic entropy-change in La0.67−xBixCa0.33MnO3 compound

Bi doped lanthanum manganites with the chemical composition of La_0.67−xBi_xCa_0.33MnO₃ (x=0$x=0$, 0.05, 0.1, 0.2) were prepared by the standard solid-state process. The Curie temperatures were measured to be 267 K for x=0$x=0$, 248 K for x=0.05$x=0.05$, 244 K for x=0.1$x=0.1$ and 229 K for x=0.2$x=0.2$ samples. It was found that the maximum value of the magnetic entropy change ∣ΔS_m∣ has reached the highest value of 6.08 J/kg K at 3 T for the composition with x=0.05$x=0.05$. Nearly the same maximum entropy change was observed for the x=0$x=0$ sample. A large decrease in the magnitude of the entropy change was observed for the x=0.2$x=0.2$ sample.     

Mössbauer studies on the superparamagnetic behavior of CoFe2O4 with a few nanometers

CoFe₂O₄ nanoparticles with a cubic spinel structure are prepared by a high-temperature thermal decomposition method. The average particle sizes are 4.6  and 5.7 nm for CoFe₂O₄ made with two kinds of solvents by TEM. Mössbauer spectra of 4.6 nm particles displayed a superparamagnetic behavior as demonstrated by a single line with zero hyperfine fields, but that of 5.7 nm particles did not at room temperature. It is considered that anisotropy energy was still more superior to thermal energy because of particle size of 5.7 nm CoFe₂O₄. Furthermore, Mössbauer spectra exhibited the typical spectrum shapes of the CoFe₂O₄ at 4.2 K. The spectrum at 4.2 K was fitted using two magnetic components of hyperfine fields _Hhf=540.4,512.6$H_{\mathrm{hf}}=540.4,512.6$ kOe and isomer shifts δ=0.40,0.30$\delta =0.40,0.30$ mm/s for 4.6 nm and _Hhf=542.7,512.8$H_{\mathrm{hf}}=542.7,512.8$ kOe and δ=0.41,0.29$\delta =0.41,0.29$ mm/s for 5.7 nm corresponding to Fe³⁺ ions at site A and site B, respectively.     

Effect of Mg substitution on electromagnetic properties of (Ni0.25Cu0.20Zn0.55)Fe2O4 ferrite prepared by auto combustion method

The ferrite compositions of (Ni_0.25−xMg_xCu_0.2Zn_0.55)Fe₂O₄ with x=0.0$x=0.0$, 0.07, 0.13, 0.18, and 0.25 were synthesized through nitrate-citrate auto-combustion method. The as-burnt powders showed the presence of crystalline cubic spinel ferrite with about 19–22 nm crystallite sizes. The resultant powders were calcined at 700 °C/2 h and pressed ferrites were sintered at 950 °C/4 h. The initial permeability, magnetic loss and AC resistivity were measured in the frequency range 10 Hz–10 MHz. The permeability and AC resistivity were found to increase and the magnetic loss decreased with Mg substitution for Ni, up to x=0.18$x=0.18$. The very high permeability in the composition x=0.18$x=0.18$, was due to better densification, lower magnetostriction constant and inner stresses, etc. The AC resistivity of the composition was also highest. The composition would be better than NiCuZn-based material for more miniaturization of multi layer chip inductor.     

Automatic registration of serial sections of mouse lymph node by using Image-Reg

The first step towards the three-dimensional (3D) reconstruction of histological structures from serial sectioned tissue blocks is the proper alignment of microscope image sequences. We have accomplished an automatic rigid registration program, named Image-Reg, to align serial sections from mouse lymph node and Peyer's patch. Our approach is based on the calculation of the pixel-correlation of objects in adjacent images. The registration process is mainly divided into two steps. Once the foreground images have been segmented from the original images, the first step (primary alignment) is performed on the binary images of segmented objects; this process includes rotation by using the moments and translation through the X, Y axes by using the centroid. In the second step, the matching error of two binary images is calculated and the registration results are refined through multi-scale iterations. In order to test the registration performance, Image-Reg has been applied to an image and its transformed (rotated) version and subsequently to an image sequence of three serial sections of mouse lymph node. In addition, to compare our algorithm with other registration methods, three other approaches, viz. manual registration with Reconstruct, semi-automatic landmark registration with Image-Pro Plus and the automatic phase-correlation method with Image-Pro Plus, have also been applied to these three sections. The performance of our program has been also tested on other two-image data sets. These include: (a) two light microscopic images acquired by the automatic microscope (stitched with other software); (b) two images fluorescent images acquired by confocal microscopy (tiled with other software). Our proposed approach provides a fast and accurate linear alignment of serial image sequences for the 3D reconstruction of tissues and organs.     

Testing the interaction model with cosmological data and gamma-ray bursts

We use the new gamma-ray bursts (GRBs) data, combined with the baryon acoustic oscillation (BAO) observation from the spectroscopic Sloan digital sky survey (SDSS) data release, the newly obtained A   parameter at z=0.6$z=0.6$ from the WiggleZ dark energy survey, the cosmic microwave background (CMB) observations from the 7-year Wilkinson microwave anisotropy probe (WMAP7) results, and the type Ia supernovae (SNeIa) from Union2 set, to constrain a phenomenological model describing possible interactions between dark energy and dark matter, which was proposed to alleviate the coincidence problem of the standard ΛCDM model. By using the Markov chain Monte Carlo (MCMC) method, we obtain the marginalized 1σ   constraints _Ωm=0.2886±0.0135${\Omega }_m=0.2886\pm 0.0135$, _rm=−0.0047±0.0046$r_m=-0.0047\pm 0.0046$, and _wX=−1.0658±0.0564$w_X=-1.0658\pm 0.0564$. We also consider other combinations of these data for comparison. These results show that: (1) the energy of dark matter is slightly transferring to that of dark energy; (2) even though the GRBs + BAO + CMB data present less stringent constraints than SNe + BAO + CMB data do, the GRBs can help eliminate the degeneracies among parameters.     

Observation of spin reorientation in layered manganites La1.2Sr1.8(Mn1−yRuy)2O7 (0.0⩽y⩽0.2) by Lorentz transmission electron microscopy

The effect of Ru substitution for Mn in bilayered oxides La_1.2Sr_1.8(Mn_1−yRu_y)₂O₇ (0?y?0.2$0?y?0.2$) was investigated by magnetization measurements and low-temperature Lorentz transmission electron microscopy. It was found that the magnetic anisotropy is controlled by the Ru content y and temperature T. The easy axis changes from 〈1 1 0〉 for the y=0$y=0$ crystal to the c  -axis for y=0.2$y=0.2$, and it rotates away from the c-  axis for the y=0.05$y=0.05$ and y=0.07$y=0.07$ crystals with decreasing temperature. Furthermore, maze-shaped magnetic domain structures were observed in the (0 0 1) thin crystals with 0.05?y?0.2$0.05?y?0.2$. Changes in domain size and structure indicate that the uniaxial magnetic anisotropy becomes stronger as Ru content y increases.     

Structural characterization and magnetization of Mg0.7Zn0.3SmxFe2−xO4 ferrites

Mg_0.7Zn_0.3Sm_xFe_2−xO₄ ferrites were prepared by the solid-state reaction method and were characterized by X-ray diffraction and magnetization measurements. A single spinel phase was obtained in the range 0.00?x?0.03$0.00?x?0.03$. The lattice parameter was found to increase at x=0.01$x=0.01$ and then decreases up to x=0.03$x=0.03$, which may indicate a distortion in the spinel lattice. The saturation magnetization was found to decrease with the increase in x up to 0.04, due to the replacement of the Fe³⁺ ions by the Sm³⁺ ions.     

Strontium ferrite nanoparticles synthesized in presence of polyvinylalcohol: Phase composition,microstructural and magnetic properties

Systematic study was devoted to the synthesis of hexagonal strontium ferrite nanoparticles employing polyvinylalcohol as stabilizing agent. Preliminary experiments allowed to select an optimal sol having molar ratio Sr²⁺/Fe³⁺=12${\mathrm{Sr}}^{2+}/{\mathrm{Fe}}^{3+}=12$, weight ratio PVA/[Sr²⁺+Fe³⁺]=1.4$\mathrm{PVA}/[{\mathrm{Sr}}^{2+}+{\mathrm{Fe}}^{3+}]=1.4$ and pH=2.1$\mathrm{pH}=2.1$. The obtained sol were transformed to gels by an evaporation of water at 100 °C and drying at 112 °C under vacuum. The subsequent calcination was carried out for 3 h at 400 °C, achieved by heating rate of 17 K/min. The obtained precursor was used for a detail study of influence of annealing conditions (temperature range 600–700 °C, annealing time 10–190 min) on the resulting properties. Semiquantitative X-ray phase analysis approved a gradual increase of the M-phase content and a gradual growth of M-phase crystallites with temperature and time. Magnetic measurements showed a distinct influence of the phase composition, namely ratio of the contents of M-phase and maghemite on the shape of the magnetic loops, while the crystallite sizes have only a slight effect.     

Enhancing entanglement of entangled coherent states by single-mode coherent superposition of photon subtraction and addition

We introduce a new entangled quantum state generated by applying single-mode coherent superposition of photon subtraction and addition (a^† cos θ + a sin θ)^m to the entangled coherent state |Ψ_±(α,0)〉$|{\Psi }_{\pm }\left(\alpha ,0\right)〉$, and then investigate the entanglement properties affected by coherent superposition operation. It is shown that this operation can be applied to enhance the entanglement of the state |Ψ₊(α,0)〉$|{\Psi }_{+}\left(\alpha ,0\right)〉$. In addition, the effects of the coherent operation is better to improve the entanglement than that of the creation operation (a^†m) for |Ψ₊(α,0)〉$|{\Psi }_{+}\left(\alpha ,0\right)〉$ in a small-amplitude regime and for |Ψ₋(α,0)〉$|{\Psi }_{-}\left(\alpha ,0\right)〉$ in any regime.