Magnetic phase diagram of GdAg1−xZnx

The magnetic phase diagram of GdAg_1?xZn_x, an intermetallic solid solution of an antiferromagnet (GdAg: T_N = 136 K) and a ferromagnet (GdZn: T_C = 269 K), has been elaborated from magnetization measurements. The antiferromagnetic phase boundary T_N(x) first passes a broad maximum meeting the ferromagnetic phase boundary T_C(x) at x₁ = 0.575 and T₁ = 72 K, where four phases coexist. On approaching (x₁, T₁) along T_N(x) the magnetization phenomena vanish. At x₁ the phase transition still has ferromagnetic appearance but proceeds into a state without spontaneous magnetic moment. Two different ferromagnetic phases (F₁, F₂) and one ferrimagnetic phase (F₃) occur in the composition intervals 0.69 < x₁ <1, and 0.61 <x₂ < 0.69 and 0.51 < x₃ < 0.61. All phase transitions seem to be of second order except th e F₁?F₂ one at x = 0.69 which is of first order. This phase line meets the paramagnetic to ferromagnetic phase boundary T_C(x) in a multicritical point with the coordinates x_m = 0.69, T_m = 123 K.Six further mixed magnetic phases, M_{1, 2, ..., 6}, are observed between x = 0.33 and 0.6 below the antiferromagnetic branch and exhibit irreversible thermodynamic properties, such as hysteresis, below about 40 K.Assuming local magnetic interactions only between nearest and next-nearest Gd neighbours, the T_N(x) and T_C(x) phase boundaries can be described fairly well by a simple model calculation using different exchange parameters for a few relevant distributions of Ag and Zn atoms.     

Intermediate valence of Ce in Ce1−xScxPd3

We present the lattice constant and susceptibility data of Ce_1?xSc_xPd₃ and report on the ESR in (Ce_1?xSc_x0.995Gd_0.005Pd₃. A transition from tetravalent cerium for x ? 0.5 to an intermediate valent state for x ? 0.3 is clearly shown by all three measuring methods.     

Raman characterization of Pb2Na1−xLaxNb5−xFexO15 and Pb0.5(5−x)LaxNb5−xFexO15 (0≤x≤1) solid solutions

The ferroelectric compounds Pb₂Na_1−xLa_xNb_5−xFe_xO₁₅ and Pb_0.5(5−x)La_xNb_5−xFe_xO₁₅ (0≤x≤1) with the tungsten bronze type structure have been investigated using Raman spectroscopy. The evolution of the spectra as a function of composition at room temperature is reported. In the frequency range 200-1000 cm⁻¹ three main A₁ phonons around 240 (υ₁), 630 (υ₂) and 816 (υ₃) cm⁻¹ were observed. The broadening of the Raman lines for high values of x originates from a significant structural disorder. This is in good agreement with the relaxor character of these compositions. The lowest-frequency part of the spectra, below 180 cm⁻¹, reveals a structural change in the studied solid solutions. The behaviour of the Raman shift of the υ₁ mode confirms that in Pb₂Na_1−xLa_xNb_5−xFe_xO₁₅, a clear anomaly occurs in the vicinity of x=0.4.     

High-resolution Fourier spectroscopy of 14N2 and 15N2 infrared emission spectrum: Analysis of the B′3Σu−-B3Πg system

The rotational analysis of some bands of the B′³Σ_u^?-B³Π_g system of nitrogen (¹⁴N₂ and ¹⁵N₂) excited in a microwave discharge and recorded under high resolution with a Fourier transform interferometer allowed the determination of molecular constants for the v = 0, 1, 2 levels in the B′³Σ_u^? state. Main equilibrium constants of the B′³Σ_u^? state for ¹⁴N₂ and ¹⁵N₂ are (in cm^?1) T_e = 5789.2178 (relative to B³Π_g (v = 0); ω_e = 1516.6239; ω_ex_e = 11.9721; B_e = 1.473 098; α_B = 0.01 664; ω_eⁱ = 1465.3549; ω_ex_eⁱ = 11.1783; B_eⁱ = 1.375 209; α_Bⁱ = 0.01 505.     

Microstructure characterization and magnetic behavior of NiAlxFe2−xO4 and Ni1−yMnyAl0.2Fe1.8O4 ferrites

NiAl_xFe_2−xO₄ and Ni_1−yMn_yAl_0.2Fe_1.8O₄ ferrites were prepared by the conventional ceramic method and were characterized by X-ray diffraction, scanning electron microscopy, and magnetic measurements. The single spinel phase was confirmed for all prepared samples. A proper explanation of data is possible if the Al³⁺ ions are assumed to replace Fe³⁺ ions in the A and B sites simultaneously for NiAl_xFe_2−xO₄ ferrites, and if the Mn²⁺ ions are assumed to replace Ni²⁺ ions in the B sites for Ni_1−yMn_yAl_0.2Fe_1.8O₄ ferrites. Microstructural factors play an important role in the magnetic behavior of Ni_1−yMn_yAl_0.2Fe_1.8O₄ ferrites with large Mn²⁺ content.     

Electronic conductivity in La1−xBaxF3−x crystals

The electronic conductivities of solid solutions La_1?xBa_xF_3?x (0 ? x ? 0.0952) were investigated up to 533 K using the Hebb-Wagner dc polarization technique. The electrochemical cell (-)La|La_1?xBa_xF_3?x|Pt(+) has been utilized with Pt as the ion-blocking electrode. Under steady-state conditions the La_1?xBa_xF_3?x solid solutions exhibit electronic conductivity. The electronic conductivity vanishes in pure LaF₃. Together with ac conductivity measurements it appears that the ionic transference number for La_1?xBa_xF_3?x (0 ? x ? 0.0952) is essentially unity over the temperature range studied.     

High Bs nanocrystalline Fe84−x−yCuxNbySi4B12 alloys (x=0.0-1.4, y=0.0-2.5)

In this study, Cu and Nb content dependences of magnetic properties for annealed Fe_84−x−yCu_xNb_ySi₄B₁₂ alloy ribbons fabricated by melt spinning were investigated. In Fe_83−xCu_xNb₁Si₄B₁₂ alloy systems, the coercivity H_c markedly decreases with increasing x and exhibits a minimum at around x=1.0-1.2, while the saturation magnetic flux density B_s shows a slight variation. In Fe_83−yCu₁Nb_ySi₄B₁₂ alloy systems, H_c markedly decreases at around y=0.5, while B_s shows a monotonic decrease. Fe₈₂Cu₁Nb₁Si₄B₁₂ nanocrystalline alloy ribbons exhibit a high B_s of 1.78 T and a low H_c of 3.2 A/m. The core losses of the present alloys at 1.0 T at 400 Hz, P_10/400, and at 1.0 T at 1 kHz, P_10/1k, are 1.3 and 4.4 W/kg, respectively.     

The magnetic properties of oxide spinel Li0.5Fe2.5−2xAlxCrxO4 solid solutions

The exchange interactions (J_BB and J_AB are the intra and the inter-sublattice exchange interactions between neighbouring spins, respectively) are obtained by using the general expressions of canting angle and critical temperature obtained by mean field theory of Li_0.5Fe_2.5−2xAl_xCr_xO₄. The expression of magnetic energy of Li_0.5Fe_2.5−2xAl_xCr_xO₄ is obtained for different spin configurations and dilution x. The saturation magnetisation of Li_0.5Fe_2.5-2xAl_xCr_xO₄ is obtained with different values of dilution x. The magnetic phase diagram of Li_0.5Fe_2.5-2xAl_xCr_xO₄ materials is obtained by high temperature series expansions (HTSEs). The critical exponent associated with the magnetic susceptibility of Li_0.5Fe_2.5−2xAl_xCr_xO₄ is deduced.     

First-principles calculations to investigate optical properties of ByAlxIn1−x−yN alloys for optoelectronic devices

First-principles density-functional theory of Full-Potential Linear Augmented Plane Wave (FP-LAPW) within local density approximation (LDA) of the optical properties of B_yAl_xIn_1−x−yN systems (with x = 0.187 and y = 0.062, 0.125 and 0.187) has been performed. Substitutional atoms of Boron induced in small amounts into the (Al_xIn_1−x)-cationic sublattice of AlInN affects the energy gap of BAlInN. The higher band gap of Al_0.375In_0.625N alloy can form a useful quantum well (QW) laser structure. A best choice of B-content, B_yAl_xIn_1−x−yN could be an alternative to Al_xIn_1−xN. The results of accurate calculations of the band structures and optical properties show the better performance characteristics belong to the structure containing B-content (y) of 12.5%. The NaCl metallic B_yAl_0.1875In_0.8125−yN has a direct character for y = 12.5%. The imaginary part of dielectric function, reflectivity, refractive index, absorption coefficient and optical conductivity are investigated well and provide reasonable results for optoelectronic devices applications.     

Synthesis and characterization of Ni1−xCoxFe2O4 nanoparticles

Ni_1−xCo_xFe₂O₄ (x=0.6, 0.8 and 0.9) nanoparticles have been synthesized with various crystallite sizes depending on the thermal treatments and composition (cobalt content) using the sol-gel combustion method. The size of nanoparticles has been controlled by thermal treatment. On the other hand, the magnetic property of the ferrite has been controlled by changing the heat treatment. Morphology and particle sizes of Ni_1−xCo_xFe₂O₄ have been studied using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The presence of functional group has been identified by Fourier Transform Infrared (FTIR) spectra. From TGA-DTA studies, the weight gains of Ni_1−xCo_xFe₂O₄ nanoparticles have been observed and it might be due to capping organic molecules with oxygen at temperatures above 200 °C. Magnetic properties of Ni_1−xCo_xFe₂O₄ particles have been analysed using VSM and it is found that saturation magnetization (M_s) has increased with particle size and has coercivity (H_c) increased initially and then decreased. The M_s and H_c values decreased with the increase of content of cobalt in Ni_1−xCo_xFe₂O₄.     

Electrical property of HfOxNy-HfO2-HfOxNy sandwich-stack films

The effects of HfO_xN_y on the electrical property of HfO_xN_y-HfO₂-HfO_xN_y sandwich-stack (signed as SS) films were investigated. Excellent electrical performances were achieved in SS films, with a high dielectric constant of 16 and a low leakage current of ∼2 × 10⁻⁸ A/cm² at 1 MV/cm. Schottky (SK) emission and Frenkel-Poole (PF) emission are found to be the dominant mechanisms for the current conduction behavior. After a long time stress, the flat-band voltage shift in the SS film is much smaller than that in a pure HfO_xN_y film indicating fewer charge traps existed in the SS film. Based on the experiments, the new SS structure is more favorable for the improvement of electrical performances than a pure HfO_xN_y or HfO₂ structure.     

Selenium dioxide: Vibrational analysis of the 3130 Å1B2-X̃1A1 absorption system

The B absorption system of the three isotopic species ⁷⁸Se¹⁶O₂, ⁸⁰Se¹⁶O₂, and ⁷⁸Se¹⁸O₂ have been comparatively studied in the vapor phase. The 0_0⁰ band is at 31955.0/31957.4/31963.9 cm^?1, respectively. The main vibrational structure is due to 1_0ⁿ2_0^m progressions, with maximum intensity at n ～ 6. The stronger progressions are those with m = 0, 1, 2, 3. The progressions are severely perturbed. The molecule is bent in both of the combining electronic states. In the ground state for the (80, 16) species, ν₁″(a₁) = 922.6, ν₂″(a₁) = 372 cm^?1. In the electronically excited state, identified as ¹B₂, ν₁′, and ν₂′ have the approximate values 649 and 258 cm^?1, respectively. Evidence is presented in favor of a double-minimum potential function with respect to Q₃′, the band 3_0¹ being observed with appreciable intensity. The height of the potential barrier is about 600 cm^?1.     

40Ca(d, α)38K and isospin

We investigate the ⁴⁰Ca(d, α_{0, 1, 2, 4})³⁸K reactions for E_d = 4.00–4.61 MeV. The α₁ and α₄ transitions are isospin forbidden. The resonant-like structures observed in the α₀, α₁, α₂, and α₄ transitions are consistent with Ericson theory. In addition we can fit a portion of the α₁, data with a few interfering Breit-Wigner resonances. The level parameters for the corresponding ⁴²Sc levels are given.     

Evidence by Raman scattering on In1−xGaxAsyP1−y of the two-mode behaviour of In1−xGaxP

We report the Raman scattering study of optical vibrations in indium rich In_1?xGa_xAs_yP_1?y epitaxial layers grown on InP. We evidence the splitting of the LO line of InP even for very small x and demonstrate it is due to the presence of gallium in the samples. These results lead us to ascribe to In_1?xGa_xP a somewhat modified two-mode behaviour and to In_1?xGa_xAs_yP_1?y a four-mode behaviour.     

Λc5He and Λc9Be charmed nuclei versus Λ5He and Λ9Be hypernuclei

A comparative study is made for _Λc⁵He and _Λc⁹Be charmed nuclei versus _Λ⁵He and _Λ⁹Be hypernuclei. The Λ_c(Λ)+α and Λ_c(Λ)+α+α systems are treated in a microscopic way. Within certain range of the Λ_cN interaction strength, the energy properties of Λ_c+α and Λ_c+α+α are calculated and discussed. Similarity between the energy spectra of the noted charmed nuclei and hypernuclei is suggested.     

The Hg2 (A3Ou− → X1Σg+) and (A31u → X1Σg+) fluorescence

The fine structure emission sepctrum near 5500 Å attributed to the Hg₂ (A³O_u^? → X¹Σ_g⁺) transition is shown to be strikingly similar to the HgCl (B²Σ⁺ → X²Σ⁺) emission spectrum sensitized by Hg(6³P_o) metastables. The correct Hg₂ (A³O_u^? → X¹Σ_g⁺) emission spectrum at 4850 Å was re-examined and confirmed to be a continuous one. It is suggested that the fine structure arose from the sensitization of a chlorine containing impurity.     

Etude par diffraction neutronique des solutions solides K1−xBixF1+2xetRb1−xBixF1+2x

Bragg neutron diffraction studies have been carried out on the fluorite type solid solutions K_1?xBi_xF_1+2x (0.50 ? × ? 0.70) and Rb_1?xBi_xF_1+2x (0.50 ? × ? 0.60). The distribution of the fluorine atoms between normal and interstitial sites is given as a function of substitution rate. A substition mechanism is proposed. Electrical and NMR results on one side and structural data on the other side are correlated. A study of the background as a function of temperature has allowed to determine the static origin of its modulation. By inelastic neutron diffusion, it has been shown that the number of carriers is weak, which involves a high mobility.     

The aΔg→XΣg magnetic dipole transition of S2

Emission spectra of the 0-0 band of the a¹Δ_g→X³Σ⁻_g magnetic dipole transition of S₂ have been observed in the near-infrared spectral region near 4400 cm⁻¹. The S₂ molecules were generated in a fast-flow system by passing S_x or S₂Cl₂ vapor in Ar carrier gas through a microwave discharge and were excited by electronic-to-electronic energy transfer from metastable singlet oxygen O₂(a¹Δ_g). Medium-resolution spectra of the b¹Σ⁺_g→X³Σ⁻_g and a¹Δ_g→X³Σ⁻_g transitions of S₂ were measured with a Fourier-transform spectrometer. By comparing the bandshape of the 0-0 band of the a→X system with a computer simulation calculated with literature data of the rotational constants of the X and a states, the origin of the 0-0 band was determined to be ν₀=4394.25±0.2 cm⁻¹.     

Magnetic ordering in EuxSr1−xSySe1−y

Specific heat and ac-susceptibility measurements are reported for Eu_xSr_1?xS_ySe_1?y samples. The critical concentrat ion for long-range magnetic ordering x_c increases with decreasing y, for y = 0.1, x_c = 1.0 holds. For samples with x < x_c a broad peak in the specific heat and a peak in the susceptibility at lower temperatures indicates a spin glass type of magnetic ordering.     

Spin resonant optical four wave mixing in Pb1−xSnxTTe epitaxial layers and in Pb1−xSnx/PbTe superlattices

Spin resonances of the third-order non-linear susceptibility of epitaxial layers of n- and p-type Pb_1?xSn_xTe and Pb_1?xSn_xTe/PbTe superlatttices have been observed by four photon mixing of the radiation of two CO₂-lasers. Precise data on the effective g-values of the electrons and holes of Pb_1?xSn_xTe were obtained. These data and the results of magneto-optical interband absorption measurements are used to obtain k·p parameters within the Mitchell and Wallis band model. In the Pb_1?xSn_xTe/PbTe superlattices, the same g-values for electrons as in the Pb_1?xSn_xTe films with the same composition x are found. Consequently, the electrons in the superlattices are confined within the Pb_1?xSn_xTe layers. Therefore the Pb_1?xSn_xTe/PbTe system forms a type I and not a staggered superlattice.