The Hall effect in amorphous (Zr0.64Ni0.36)1−x M x alloys (M=Al,Ga)

Values of the room temperature Hall coefficients and electrical resistivity of amorphous melt spun (Zr_0.64Ni_0.36)_1–x Al _x and (Zr_0.64Ni_0.36)_1–x Ga _x alloys forx=0–0.25 are reported. Addition of Al or Ga to Zr_0.64Ni_0.36 dramatically increases the already positive Hall coefficient of this alloy and also increases the electrical resistivity and crystallization temperature.     

金属玻璃(Cu1-xNix)33Zr67合金的低温电阻率

本文研究了金属玻璃(Cu_1-xNi_x)₃₃Zr₆₇合金的低温电阻输运特性。在较宽的温区(2—273K)测试了电阻率,测量结果符合Mooij判据。样品电阻率随温度的变化行为与双能级隧道模型符合较好。 关键词：     

Influence of the solvent matrix on the overlapping of the absorption and emission bands of solute fluorescent dyes

Electrical resistivity and magnetic susceptibility of amorphous Ni_xZr_1−x alloys obtained by the “melt spinning” method have been measured in order to study crystallization kinetics. The correlation between the degree of negativity of the temperature coefficient of resistivity and the stability of amorphous alloys was observed. The studied relation between stability and the coefficient indicated that β may be treated as a measure of the structural changes occuring during crystallization.     

Novel synthesis of NixZn1?xFe2O4 (0?≤?x?≤?1) nanoparticles and their dielectric properties

Nanocrystalline Ni _x Zn_1−x Fe₂O₄ (0 ≤ x ≤ 1) ferrite powders with average particle size 15–20 nm have been successfully prepared at a very low temperature (180 °C) by a novel auto combustion process using citric acid and ethylenediamine as a coordinating agent and bridging ligand, respectively. Phase purity of the solid solutions has been confirmed by X-ray diffraction. Morphological characterizations of the prepared samples were performed by high resolution transmission electron and field emission scanning electron microscopy. Extensive Fourier transformed infrared spectroscopic characterization has been carried out to identify the plausible mechanism of the synthesis process. Composition-dependent electrical properties (resistivity and dielectric constant) of the synthesized solid solution have been investigated. Interestingly, a non-linear variation of dielectric permittivity with respect to composition has been observed. The room temperature electrical resistivity as well as the dielectric permittivity of Ni_0.5Zn_0.5Fe₂O₄ was found to decrease with the decrease of particle size.     

Deformation behavior of Zr-based bulk metallic glass and composite in the supercooled liquid region

A Zr-based bulk metallic glass (BMG) with a composition of (Zr₇₅Cu₂₅)_78.5Ta₄Ni₁₀Al_7.5 and a bulk metallic glass matrix composite (BMGC) with a composition of (Zr₇₅Cu₂₅)_74.5Ta₈Ni₁₀Al_7.5 have been prepared by copper-mold casting. The compressive deformation behavior of the BMG and BMGC was investigated in the supercooled region at different temperatures and various strain rates ranging from 8×10⁻⁴ s⁻¹ to 8×10⁻² s⁻¹. It was found that both the strain rate and test temperature significantly affect the deformation behavior of the two alloys. The deformation follows Newtonian flow at low strain rates but non-Newtonian flow at high strain rates. The deformation mechanism for the two kinds of alloys was discussed in terms of the transition state theory. Supported by the National Natural Science Foundation of China (grant Nos. 50471060 and 50635020)     

Low concentration of the superconducting phase and thermoelectric power in 90 K superconductors

The thermoelectrical power (TEP) and the electrical resistivity behaviour of three 90 K superconductors viz, Y₁Ba₂Cu₃O_7−x , Sm₁Ba₂Cu₃O_7−x and Gd₁Ba₂Cu₃O_7−x , after the specimens were quenched from the sintering temperature (920°C) to 77 K, are reported. Interestingly the Y₁₂₃ specimen, which has the presence of trace amount of the orthorhombic phase in an otherwise tetragonal phase and does not show a superconducting transition down to 77 K shows zero TEP around 82 K, theT _c for the well oxygenated specimen. The Sm and Gd specimens on the other hand show completely tetragonal structure, semiconducting behaviour in resistivity and no zero TEP up to 77 K. It is argued that the critical concentration of the superconducting phase necessary to make the TEP zero is much smaller than that required for zero resistivity.     

Influence of copper intercalation on the resistive state of compounds in the Cu-HfSe<Subscript>2</Subscript> system

Polycrystalline samples of intercalated compounds Cu _x HfSe₂ have been synthesized for the first time and their electrical resistivity has been measured at both direct current and alternating current (with a frequency ranging from 200 Hz to 150 kHz) in the temperature range 80–300 K. It has been shown that the intercalation of copper atoms between three-layer Se-Hf-Se blocks leads to an increase in the electrical resistivity of the samples, as well as to a more pronounced activated character of the temperature dependence of the electrical resistivity. A time dependence of the electrical resistivity of the Cu _x HfSe₂ samples at room temperature, which is associated with the presence of copper ions in the sample, has been determined.     

Kinetic properties of Ni<Subscript>3</Subscript>Al<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> alloys in the range of transition from band to spin-localized ferromagnetism

The kinetic properties of ferromagnetic Ni₃Al_{1 − x} Mn _x alloys with _x ≤ 0.6 are studied at T ≤ 800 K and H ≤ 7 MA/m. The behavior of the electrical resistivity, the thermopower, the magnetoresistance, the Hall effect, and the spontaneous Hall effect are analyzed in the range of transition from band (Ni₃Al) to spinlocalized (Ni₃Mn) ferromagnetism at x ∼ 0.15.     

Electrical and magnetic properties of [(CoFeZr)x(Al2O3)1 ? x/(α-SiH)]n multilayer structures

The concentration dependences of the electrical resistivity and complex permeability of [“(Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} ”/“α-Si: H”] _n multilayer structures and (Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} composites have been studied. It has been established that introduction of a semiconductor interlayer into the (Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} composites substantially decreases the electrical resistivity of [“(Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} ”/“α-Si: H”] _n multilayer structures. The concentration dependences of the real and imaginary parts of the complex permeability of the [“(Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} ”/“α-Si: H”] _n nanomultilayer structures substantially differ from those of the (Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} composites. The real part of the complex permeability of the [“(Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} ”/“α-Si: H”] _n nanomultilayer structures follows the curve with a minimum near the percolation threshold of the composite, and the imaginary part smoothly decreases as the ferromagnetic phase concentration increases. The results obtained are explained by the increase in the bifurcation temperature due to the conduction electrons of the semiconductor interlayer, which favor magnetic ordering of ferromagnetic grains.     

Comparative analysis of the effect of La and Co on the superconductivity and energyband spectrum of YBa2Cu3Oy for different oxygen contents

Temperature dependences of the resistivity and Seebeck coefficient of Y(Ba_1−x La_x)₂Cu₃O_y and YBa₂Cu_3−x Co_xO_y samples (x=0–0.25) have been measured under maximum sample saturation with oxygen, as well as following their anneal in an oxygen-deficient atmosphere. The T _c (x) dependences for as-prepared samples were found to pass through a maximum at x=0.05, which persists after annealing for Y(Ba_1−xLa_x)₂Cu₃O_y and disappears for YBa₂Cu_3−x Co_xO_y. A phenomenological model of the band spectrum in normal phase has been used to determine the parameters of the conduction band and of the carrier system, and to analyze their variation with the dopant type and content, as well as with annealing. Despite the differences observed in the T _c (x) dependence, the critical temperatures for all the sample series studied were found to correlate with the conduction-band effective width. The mechanism of the effect of impurities on the band-structure parameters and the reasons for the different influence of annealing on the properties of Y(Ba_1−x La_x)₂Cu₃O_y and YBa₂Cu_3−x Co_xO_y are discussed. Fiz. Tverd. Tela (St. Petersburg) 41, 389–394 (March 1997)     

Effect of substrate temperature on electrical and magnetic properties of epitaxial La1−x Pb x MnO3 films

Epitaxial La_1−x Pb _x MnO₃ (LPMO) thin films, grown on (100) SrTiO₃ substrates by laser ablation technique at different temperatures between 600 and 850°C, have been characterized for electrical and magnetic properties. The temperature dependence of resistivity showed that the metal-insulator transition temperature (T _MI) decreases with increasing substrate temperature, which has been attributed to decrease in Pb content in the filsm. The YBa₂Cu₃O _x /La_1−x MnO₃ heterostructures, exhibiting both superconductivity and ferromagnetism, have been fabricated.     

Magnetic interference effect in amorphous D-band metals with high electrical resistivity

Systematic occurence of low temperature resistivity anomalies (upturn) in amorphous alloys Zr₅₀Cu₅₀, Zr₇₅Ni₂₅, and Y₇₅A?₂₅ containing up to 4 at .% Gd is observed. Detailed analysis of ‘background’ impurity (other than Gd) effects on the electrical resistivity of the alloy host Zr₅₀Cu₅₀ provides unambiguous evidence that the anomalies are due solely to the Gd ions. The present results are interpreted in terms of conduction electrons with short mean free path scattering from nearest neighboring pairs of Gd spins. Predictions derived from the diffraction type model of magnetic interference, however, fail to describe all the results on metals with high electrical resistivity. Data on Zr₅₀Cu₅₀ containing Fe and Mn are also discussed.     

Mechanism of the antihysteresis behavior of the resistivity of graphene on a Pb(Zr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ti<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>)O<Subscript>3</Subscript> ferroelectric substrate

A numerical model has been proposed to explain the antihysteresis behavior of the resistivity of graphene on a Pb(Zr _x Ti_{1 − x} )O₃ ferroelectric substrate with a change in the gate voltage. The model takes into account the screening of the electric field in the substrate by electrons trapped in states connected with the graphene-ferroelectric interface and describes the previously obtained experimental dependences. The estimates can be important for creating elements of new-generation energy-independent memory using two stable resistivity values that appear in the antihysteresis effect; logical 0 and 1 are assigned to these two values.     

Band spectrum modification and dynamics of superconducting properties in the Y1?xCaxBa2Cu3?xZnxOy system

Temperature dependences of the electrical resistivity and Seebeck coefficient have been studied on a series of samples of the Y_1−x Ca_xBa₂Cu_3−x Zn_xO_y system (x = 0–0.25). The effect exerted by a combination of the impurities under study on the properties of the normal phase was established. The experimental data obtained were analyzed quantitatively in terms of a phenomenological model of electron transport. The parameters of the band responsible for conduction in the normal phase and of the carrier system were calculated for all the samples studied. A mechanism of zinc doping-induced band structure modification in the yttrium system is proposed that accounts for the transformation of the temperature dependence of the Seebeck coefficient and the dynamics of superconducting properties in this compound. __________ Translated from Fizika Tverdogo Tela, Vol. 47, No. 3, 2005, pp. 422–426. Original Russian Text Copyright ? 2005 by Elizarova, Martynova, Potapov, Gasumyants, Mezentseva.     

Electrical resistivity of K-based liquid binaries

The study of the electrical resistivity of alkali K-based liquid binaries, viz, K _1−x Na _x, K _1−x Rb _x, and K _1−x Cs _x have been made by well recognized model potential. The most recent local field correction functions due to Farid et al. (F) and Sarkar et al. (S) are used for the first time in the study of electrical resistivity of liquid binary mixtures and found suitable for such study. The results due to the inclusion of Sarkar et al.’s local field correction function are found superior to those obtained due to Farid et al.’s local field correction function. The present results compare well the experimental data. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 40–44, August, 2006.     

Effect of the spin and valence states of cobalt ions on the kinetic properties of Ho1 ? xSrxCoO3 ? δ and Er1 ? xSrxCoO3 ? δ compounds

The electrical conductivity and Seebeck effect in ceramics based on cobaltites Ho_{1 − x} Sr _x CoO_{3 − δ} (x = 0.65, 0.75, 0.85, 0.95) and Er_{1 − x} Sr _x CoO_{3 − δ} (x = 0.75, 0.85, 0.95) with a perovskite-like structure have been investigated in the temperature range T > 77 K. All the compounds under study are characterized by the variable-range-hopping conductivity with the temperature dependence of the electrical resistivity corresponding to the Mott law. It has been found that, in the Ho_0.35Sr_0.65CoO_{3 − δ} compound, thermally excited Co³⁺ ions contribute to the electrical conductivity with an increase in temperature to 250 K. The Seebeck coefficient of the systems studied decreases as the strontium concentration and temperature increase. It has been shown that, for an adequate explanation of this behavior, proper allowance must be made for the splitting of the 3d levels, as well as for the charge disproportionation of the cobalt ions.     

Superconductivity in the BaPb1−x Bi x O3 system

Superconductivity properties of the BaPb_1−x Bi _x O₃ system have been investigated by precise measurements of electrical resistivity and Hall coefficient in specimens prepared by the hot press technique. Sharp superconducting transitions have been observed in those specimens, indicating the homogeneities of the specimens thus prepared. superconductivity has been observed for 0.05<x≦0.35 and a maximum critical temperature of 11.7 K has been observed atx=0.25. The carrier concentration deduced from the Hall coefficient has been found to show nearly the samex dependence as does the critical temperature. The upper critical field has been determined from the magnetic field dependence of the lowcurrent-density resistivity. Discussions are given about the superconductivity in the BaPb_1−x Bi _x O₃ system on the basis of the experiment results.     

Electrical properties of amorphous (Co45Fe45Zr10)x(Al2O3)1?x nanocomposites

The electrical properties of (Co₄₅Fe₄₅Zr₁₀)_x(Al₂O₃)_1−x granular nanocomposites have been studied. The concentration dependences of electrical resistivity are S-shaped (in accordance with the percolation theory of conduction) with a threshold at a metallic component concentration of ∼41 at. %. An analysis of the temperature behavior carried out in the range 300–973 K revealed that structural relaxation and crystallization of the amorphous phase are accompanied by a decrease in the electrical resistivity of the composites above the percolation threshold and by its increase below the percolation threshold. For metallic phase concentrations x<41 at. %, variable range hopping conduction over localized states near the Fermi level was found to be dominant at low temperatures (77–180 K). A further increase in temperature brings about a crossover of the conduction mechanism from Mott’s law ln(σ) ∝ (1/T)^1/4 to ln(σ) ∝ (1/T)^1/2. A model of inelastic resonance tunneling over a chain of localized states of the dielectric matrix was used to find the average number of localized states involved in the charge transport between metallic grains. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 11, 2004, pp. 2076–2082. Original Russian Text Copyright ? 2004 by Kalinin, Remizov, Sitnikov.     

Transport phenomena of SmSe1−x As x

Results are presented on the measurements of unit cell parameter and electrical resistivity under pressure on SmSe_1−x As _x forx=0.1, 0.2, 0.3 and 0.4. The electrical resistivity values are found to be decreasing with increase of pressure and also with increase of arsenic concentration. The semiconductor to metallic transition is induced by chemical alloying of SmSe with SmAs similar to that observed under pressure. The electrical resistivity values are also calculated which are in good agreement with the experimental values. In this calculation, the carrier mobility is of negative sign and so the sample SmSe_1−x As _x is found to ben-type semiconductor.     

Magnetic and electrical properties of Mg1−x CuxO solid solutions and magnetic shielding in Cu-Mg1−x CuxO structures

Mg_1−x Cu_xO solid solutions having an NaCl structure with 0⩽x⩽0.20 are synthesized and Cu-Mg_1−x Cu_xO structures are prepared for superconductivity studies. The magnetic susceptibility χ, electron paramagnetic resonance (EPR), and electrical conductivity of the solid solutions are studied at temperatures of 5–550 K. It is shown that χ ⁻¹(T) obeys the Curie-Weiss law with a paramagnetic Curie temperature Θ close to zero and an effective magnetic moment μ _eff=1.9 μ _B, close to the 1.73 μ _B of a Cu²⁺ ion with spin S=1/2. The width ΔH of the EPR line depends weakly on temperature and increases as x is raised. The volume narrowing of the EPR linewidth ΔH is used to estimate the exchange interaction parameter, 3×10⁻⁴ eV. The g-factor is close to 2 and is temperature independent. The electrical conductivity of Mg_1−x Cu_xO at T=300 K is ≈10⁻¹¹–10⁻¹² Ω⁻¹ cm⁻¹ for x=0 and increases to 10⁻⁵–10⁻⁶ Ω⁻¹ cm⁻¹ for x=0.15–0.20. The conductivity is p-type. Magnetic shielding is observed in Cu-Mg_1−x Cu_xO structures with x=0.15 and 0.20. The possible connection of this phenomenon with interference superconductivity in the contact layer of the structure is discussed. Fiz. Tverd. Tela (St. Petersburg) 41, 293–296 (February 1999)