Magnetic annealing effect in amorphous Fe100-xBx and Co100-xBx binary alloys

The uniaxial magnetic anisotropy induced by magnetic annealing was studied for rapidly quenched amorphous Fe_100-xB_x (12?x?25) and Co_100-xB_x (17?x?30) alloys. The value of induced uniaxial anisotropy constant K_ui increased with increasing B content from 1 x 10³ erg/cm³ at x = 12 to about 4 x 10³ erg/cm³ at x = 25 in Fe_100-xB_x alloy s exhibiting an inflection around x=20. While the value of K_ui in Co_100-xB_x alloys exhibits a maximum of about 6 x 10³ erg/cm³ aro round x=20. The compositional dependence of K_ui for both alloy systems can be explained roughly by the model of the directiona; occupation of B atom between ferromagnetic atoms.     

Electromechanical properties and dielectric behavior of (Bi1/2Na1/2)(1−1.5x)BixTiO3 lead-free piezoelectric ceramics

Bismuth doped bismuth sodium titanate ceramics [(Bi_1/2Na_1/2)_(1−1.5x)Bi_xTiO₃, x=0 to 0.06] were prepared, and the resulting effects on the microstructure and dielectric properties were examined. All of the Bi-doped ceramics exhibited a single phase of perovskite structure with rhombohedral symmetry. The poling leakage current was significantly reduced by the doping of Bi, facilitating the poling process of the ceramics. The doping with Bi enhances the piezoelectric properties and increases the dielectric constant and the dielectric loss of the ceramics. At 2 mol% Bi-doping level, the ceramics exhibit a large remanent polarization of 47 μC/cm² and a relatively low coercive field of 71 kV/cm, while their d₃₃ and k_p reach a maximum value of 95 pC/N and 21%, respectively.     

Study of the [(Co45Fe45Zr10)x(Al2O3)100−x/a-Si:H]m multilayer nanostructure by polarized neutron reflectometry

Polarized neutron reflectometry was used to investigate the amorphous multilayer nanostructures [(Co₄₅Fe₄₅Zr₁₀)_x(Al₂O₃)_100−x/a-Si:H]_m, whose magnetic properties are dependent on the concentration of the magnetic constituent (x=34, 47 and 60 at%) as well as on the thicknesses of the metal-dielectric (Co₄₅Fe₄₅Zr₁₀)_x(Al₂O₃)_100−x and semiconductor a-Si:H layers. The average magnetization of the individual magnetic layer is found to be inhomogeneous with the magnetically active central part and two magnetically dead parts at the interfaces.     

Magnetic characterization of Bi(Fe1 − xMnx)O3

Bi(Fe_1 − xMn_x)O₃ ceramics (x up to 0.3) were prepared by rapid sintering. Weak ferromagnetism with two magnetic anomalies at low temperatures was observed for Bi(Fe_0.95Mn_0.05)O₃ and Bi(Fe_0.9Mn_0.1)O₃. From temperature-dependent magnetic relaxation measurements, the anomalies at 20 K and 100 K are related to the freezing of cluster spin glass.     

Field annealing effect on amorphous (FexCo1-x)85Nb15 alloys

The magnetic anisotropy induced by magnetic field annealing was examined for amorphous (Fe_xCo_1-x)₈₅Nb₁₅ alloys produced by a sputtering technique. An appreciably large uniaxial anisotropy was observed even at x = 0. The anisotropy constant (K_u) obtained was 2.3x10³ erg/cm³ at x=0, and it increased with x, showing a maximum of about 5.4x10³ erg/cm³ near x = 0.2. This compositional change in K_u was explained in terms of the directional ordering of magnetic Fe-Co atom pairs under the negative nonmagnetic interaction energy leading to a precipitation.     

Evolution des proprietes de transport des solutions solides M1−xM′xF2+x (M=Sr,Pb; M′=Sb,Bi) ET M1−xM″xF2+2x (M″=Zr,Th) pour les faibles taux de substitution

A detailed study of the transport properties of the solid solutions M_1?xM′_xF_2+x (M=Sr, Pb; M′=Sb, Bi) and M_1?xM″_xF_2+2x (M″=Zr, Th) has been carried out for x<0.10. Contrary to solid solutions of strontium, solid solutions of lead show for a very small value of x (x = 0.10 forPb_1?xM′_xF_2+x, x = 0.005 for Pb_1?xM″'_xF_2+2x) a minimum of conductivity associated with a maximum of activation energy. Hypotheses are proposed to explain the results.     

Diamagnetic properties of tetrahedrally coordinated Ge1-xSx and Ge1-xSex amorphous alloys

Measurements of the diamagnetic susceptibility χ at room temperature are reported for Ge_1-xS_x and Ge_1-xSe_x amorphous alloys as a function of composition. The composition dependence of χ is shown to reflect the corresponding changes in the average gap E_g and it is concluded that the dia diamagnetic enhancement observed in tetrahedrally bonded amorphous semiconductors is caused by a decrease in the interband matrix element in the Van-Vleck paramagnetic susceptibility term with bond angle distortion rather than changes in E_g.     

Spin-glass-like behaviour of the mixed spinel systems MnxZn1-xCr2O4 and Mn0.75Mg0.25(Cr1-yVy)2O4

NMR and susceptibility measurements have been made on a randomly mixed insulating ferrimagnet and antiferromagnet, Mn_xZn_1-xCr₂O₄. The thermoremanence and the induced unidirectional anisotropy were observed for concentrations lower than x = 0.80, after field cooling. The compound Mn_0.75Mg_0.25Cr₂O₄ shows similar behaviour. When the latter is doped with V³⁺ at the B sites, its magnetic anisotropy increases strongly, but the change in the unidirectional anisotropy is smooth.     

Magnetic interactions between Fe(III) ions in the solid solutions CuM1 − xFexS2 (M = Al,Ga, In) and AgM1 − xFexO2 (M = Al,Ga).

Magnetic properties of CuM_{1 ? x}Fe_xS₂ (M = Al, Ga, In) and β-AgM_{1 ? x}, Fe_xO₂ (M = Al, Ga) solid solutions have been studied by Mössbauer spectroscopy (only on CuGa _{1 ? x}Fe_xS₂), magnetization measurements and EPR spectroscopy.In the structures studied all ions have tetrahedral co-ordination.The magnetic interactions between Fe(III) ions are shown to be very strong for nn sites ($\text{J}\text{k}$～100 K). More distant exchange interactions are found to fall off rather slowly as the distance between Fe(III) ions increases and are suggested to depend essentially on the number of bonds traversed.     

Sn1−xBixO2 and Sn1−xTaxO2 (0≤x≤0.75): A first-principles study

The structural, elastic, electronic and optical (x=0) properties of doped Sn_1−xBi_xO₂ and Sn_1−xTa_xO₂ (0≤x≤0.75) are studied using the first-principles pseudopotential plane-wave method within the local density approximation. The independent elastic constants C_ij and other elastic parameters of these compounds have been calculated for the first time. The mechanical stability of the compounds with different doping concentrations has also been studied. The electronic band structure and density of states are calculated and the effect of doping on these properties is also analyzed. It is seen that the band gap of the undoped compound narrowed with dopant concentration, which disappeared for x=0.26 for Bi doping and 0.36 for Ta doping. The materials thus become conductive oxides through the change in the electronic properties of the compound for x≤0.75, which may be useful for potential application. The calculated optical properties, e.g. dielectric function, refractive index, absorption spectrum, loss-function, reflectivity and conductivity of the undoped SnO₂ in two polarization directions are compared with both previous calculations and measurements.     

Electrochemical lithium incorporation into WO3 and MoO3 thin films

The generally accepted mechanism of electrochromic phenomena into WO₃ thin films involves the simultaneous injection of cations and electrons to form a tungsten bronze M_xWO₃, e.g. H_xWO₃,Li_xWO₃. Electrochromic cells of the type ITO MO₃/LiClO₄(M) in propylene carbonate/Pt, where M = W or MO and MO₃ is an amorphous thin film have been used. Different amounts of charges have been injected through these cells by electrochemical means at room temperature. The variations of the MO₃ electrode potential with the injected charge are in good agreement with the assumption of the formation of Li_xMO₃ compounds. The free enthalpies of formation of these bronzes have been calculated. The behavior of thin film electrodes seems to be intermediate between amorphous and crystallized bulky materials. Some measurements of electrode potential have also been carried out with crystallized thin films of sputtered WO₃.     

Structure, microstructure and ionic conductivity of the solid solution LiTi2−xSnx(PO4)3

The Nasicon compounds with the composition LiTi_2−xSn_x(PO₄)₃ (x=0-1.8) were synthesised by the solid state reaction. Their structures were determined from X-ray powder diffraction using Rietveld analysis. All the compositions present the space group R-3c. The refinements show that the Ti and Sn cations are statistically distributed over the same position while the Li ones are exclusively located on the M1 site. The lattice constants a and c exhibit linear variation over the whole composition range. The bond lengths are in accordance with those of other Nasicon structures. The SEM micrographs of the samples show relative porous microstructures. The ionic conductivity is about 10⁻⁴-10⁻⁵ S cm⁻¹; for the activation energy, a typical value of 0.32 eV is obtained for x=0.6 composition whereas significant deviation from linearity in the temperature dependence of the dc conductivity, is observed for the Sn-rich ones. This tendency is discussed along with the structural features.     

Electrical conductivity of (Bi,Pb)2MO4 (M = Pd,Pt) linear chain compounds

Partial oxidation of Pd in Bi₂PdO₄ is achieved by substitution of Pb²⁺ for Bi³⁺ up to Bi₁₉₁Pb₀₀₉PdO₄, partial oxidation is necessary to stabilize the isostructural Pt compound, Bi_1?xPb_xPtO₄ within the range 0.33 ? x ? 0.52. In both cases, the tetragonal cell c parameter, therefore metal-metal distance $\text{(d}{}_{\mathrm{<mtext>M?M</mtext>}}\text{=}\text{c}\text{2}\text{)}$, decreases linearly with increasing mean oxidation degree (MOD) of transition metal atom For the insulator B1₂CuO₄, no substitution occurs Powder electrical conductivity measurements of the partially oxidized compounds show that these materials are semiconductors Platinum compounds exhibit relatively high conductivities $\text{(σ?10 (Ω}\text{cm}\text{)}{}^{\mathrm{?1}}\text{)}$ and low activation energies (?0 02 eV) with small variations with x Palladium compounds exhibit lower conductivities which linearly increases with MOD These electronic properties are comparable with those of the most one-dimensional Pt or Pd chain conductors.     

Effect of 3d metal ion doping on the structure and superconductivity of (Tl0.5Pb0.5)Sr2CaCu2O7

(Tl_0.5Pb_0.5)Sr₂Ca(Cu_2−xM_x)O₇ (M=Co, Ni and Zn) have been synthesized and investigated by means of X-ray diffraction, scanning electron microscope, electrical resistivity and magnetic susceptibility measurements. X-ray diffraction patterns show that all studied samples contain the nearly single ‘1212’ phase. They crystallize in a tetragonal unit cell with a=3.8028-3.8040 Å and c=12.0748-12.1558 Å. In (Tl_0.5Pb_0.5)Sr₂Ca(Cu_2−xM_x)O₇ system (M=Co or Ni), the superconducting critical temperature T_c decreases linearly with both Co and Ni concentrations and the rate of T_c decrease is around −6.5 and −7.0 K/at%, respectively. For (Tl_0.5Pb_0.5)Sr₂Ca (Cu_2−xZn_x)O₇ system, the dependence of T_c on the Zn dopant concentration deviates from a linear behavior and the Zn substitution suppresses T_c much less (−2.5 K/at%) than the Co and Ni substitutions. The suppression in T_c in Co and Ni doped samples are attributed to the magnetic pair-breaking mechanism and the reduction in the carrier concentration. The suppression of T_c in Zn doped samples is not caused by the reduction in carrier concentration which should remain constant, but rather due to nonmagnetic pair-breaking mechanism induced by disorder as well as the filling of the local Cu d_x²−y² state due to the full d band of Zn ions.     

Effect of Nb addition on the structure and soft magnetic properties of melt-spun Co69Fe7Si14B10 alloy

Melt-spun ribbons of Co₆₉Fe₇Si_14−xNb_xB₁₀ alloys with x=0, 2 and 4 have been prepared and characterized for structure and soft magnetic properties. Ribbons with x=0 and x=2 are found to be completely amorphous whereas the ribbon with x=4 contains irregular shaped faulted Co₂Si orthorhombic phase with grain size of about 100 nm. Nb addition is found to decrease the degree of amorphicity and induce perpendicular anisotropy, deteriorating the soft magnetic and magnetoimpedance properties.     

Ferromagnetism in amorphous Ge1−xMnx grown by low temperature vapor deposition

Magnetic properties of amorphous Ge_1−xMn_x thin films were investigated. The thin films were grown at 373 K on (100) Si wafers by using a thermal evaporator. Growth rate was ∼35 nm/min and average film thickness was around 500 nm. The electrical resistivities of Ge_1−xMn_x thin films are 5.0×10⁻⁴∼100 Ω cm at room temperature and decrease with increasing Mn concentration. Low temperature magnetization characteristics and magnetic hysteresis loops measured at various temperatures show that the amorphous Ge_1−xMn_x thin films are ferromagnetic but the ferromagnetic magnetizations are changing gradually into paramagnetic as increasing temperature. Curie temperature and saturation magnetization vary with Mn concentration. Curie temperature of the deposited films is 80-160 K, and saturation magnetization is 35-100 emu/cc at 5 K. Hall effect measurement at room temperature shows the amorphous Ge_1−xMn_x thin films have p-type carrier and hole densities are in the range from 7×10¹⁷ to 2×10²² cm⁻³.     

Transport properties of MoTe2−x and MoSe2−x compounds between 130 and 300°K

Thermoelectric power and Hall coefficient values were measured on compact polycrystalline samples from the MoTe_2?x and MoSe_2?x systems. It appears that qualitatively the temperature dependence of the Seebeck coefficient is not very different from that of crystalline semiconductors. The Seebeck coefficient is positive indicating hole conduction whilst Hall coefficient measurements on the same samples show negative values implying that conduction is by electrons. Singularities in the graphs plotted as a function of the composition x are found for both MoTe_2?x and MoSe_2?x systems. These results are discussed in terms of a quasi amorphous semi-conductor model.     

非晶态(Fe1-xCox)77.5Nd4B18.5合金的电阻率的压力系数和压力弛豫研究

在０．０００１－２．４ＧＰａ流体静压力范围详细研究了非晶(Fe_1-xCo_x)_77.5Nd₄B_18.5（０≤ｘ≤１．０）合金的电阻率与压力的关系，得到该非晶合金电阻率的压力系数随组分ｘ变化的规律。结果表明：用少量的钴（ｘ＝０．２）替代铁，不会影响其硬磁性和热稳定性，同时却可减小电阻率的压力系数，从而增强电磁性能在压力下的稳定性。此外还观测到在０．５１ＧＰａ保压３－２４h的结构弛豫，进一步求出该非晶台金电阻率的压力弛豫时间对组分ｘ的依赖关系。 关键词：     

Superconductivity coexisting with ferromagnetism in mixed-valence Mn doped La1.85−(4/3)xSr0.15+(4/3)xCu1−xMnxO4

The effect of Mn substitution for Cu in mixed-valence Mn doped La_{1.85−(4/3)x}Sr_0.15+(4/3)xCu_1−xMn_xO₄ (x=0.06) has been investigated by electric resistivity, magnetization and electron spin resonance experiments. Coexistence of superconductivity and ferromagnetism was observed.     

EPR investigations of oxidation effects in (V1−xMox)2−δO3

Electron paramagnetic resonance (EPR) investigations has been carried out on the new family of molybdenum doped vanadium sesquioxides (V_1−xMo_x)_2−δO₃. The oxidation effects were monitored from the rate of paramagnetic V⁴⁺ created when the sample is exposed to the air. The effects of the oxidation time, sample temperature, and annealing at 1000 °C under a diluted hydrogen atmosphere on the EPR signal features are analyzed. The V⁴⁺ concentration in the oxidized samples is determined and the relaxation effects driven by the conduction electrons are pointed out from the thermal behaviour of the EPR line features. EPR spectra of all the oxidized samples also reveal a small ferromagnetic contribution strongly correlated with the V⁴⁺ content.