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The introduction of carbon interstitials into high-entropy alloys (HEAs) provides an effective way to improve their properties. However, all such HEA systems explored so far are limited to those with the face-centered-cubic (fcc) structure. Here we report the structural, mechanical and physical properties of the refractory (Nb0.375Ta0.25Mo0.125W0.125Re0.125)100−xCx HEAs over a wide x range of 0 ≤ x ≤ 20. It is found that, whereas the starting HEA (x = 0) is composed of a major body-centered-cubic (bcc) phase with significant impurities, the bcc phase fraction increases with the C concentration and achieves almost 100% at x = 20. Moreover, the increase of C content x results in an expansion of the bcc lattice, an enhancement of the microhardness, an increase in residual resistivity and a small variation of density of states at the Fermi level. All these features are consistent with the expectation that carbon atoms occupy the interstitial site. For x ≥ 11.1, the X-ray photoelectron spectroscopy indicates the bond formation between the carbon and metal atoms, suggesting that some carbon atoms may also reside in the lattice site. In addition, a semiquantitative analysis shows that the enhanced mixing entropy caused by carbon addition plays a key role in stabilizing the (nearly) single solid-solution phase. Our study not only provides the first series of carbon interstitial HEAs with a bcc structure, but also helps to better understand the alloying behavior of carbon in refractory HEAs.

In this work, a series of FeS1-xTex (0 ≤ x ≤ 0.15) single crystals were successfully synthesized by a hydrothermal method for the first time. According to the measurement of in-plane resistivity, Hall effect, and magnetoresistance (MR), we find that the superconducting transition temperature Tc is rapidly suppressed with the increasing Te substitution, and finally the superconductivity disappears when x > 0.05. With the substitution of Te for S, the residual resistivity ρ0 increases while the residual resistivity ratio (RRR) decreases monotonously. Meanwhile, the MR of FeS1-xTex is also reduced by Te doping. All these results reveal that the Te substitution introduces more impurity scattering. In consequence, the non-linear field-dependent of Hall resistivity ρxy at low temperature region is suppressed and a linear behavior is restored upon Te doping. The negative Hall coefficients RH for all the FeS1-xTex samples suggest that the electron-type carrier dominates the electrical conduction. Moreover, the MR of FeS1-xTex obviously follows Kohler’s law, indicating the isotropic scattering rates in the Fermi surface.

Undoped, Eu- and La-doped CuS nanoparticles stabilized by l-cysteine were synthesized by a low-temperature soft aqueous route. Their structural properties were investigated by X-ray powder diffraction, their morphological properties were scrutinized using scanning electron microscopy, their microstructural properties were carried out using transmission electron microscopy, their optical properties were examined using ultraviolet–visible spectroscopy, and their electrical properties were studied using complex impedance spectroscopy. It was found that Cu0.99La0.01S nanoparticles exhibit the smallest particle size, the highest optical bandgap, the highest values of electrical conductivity and dielectric constant, and the lowest values of dielectric loss tangent when compared with CuS and Cu0.99Eu0.01S nanoparticles. To investigate the effect of the as-synthesized nanoparticles on the superconducting properties of bismuth-based compound ((Bi,Pb)2Sr2Ca2Cu3Oδ), its structural properties were examined by X-ray powder diffraction, its transport properties were analyzed by the standard four-probe technique, its intrinsic properties were investigated using the Aslamazov–Larkin approach and its pinning properties were studied using the thermally activated flux flow model. It was found that Cu0.99La0.01S added sample exhibits the highest Bi-2223 phase concentration, the lowest residual resistivity, the highest critical transition temperature, the lowest value of coherence length, the highest values of penetration depth, upper critical magnetic field and critical current density, the narrowest shift of the zero-resistivity temperature, the highest effective pinning energies and the highest global critical current densities, when compared with pure, CuS and Cu0.99Eu0.01S added samples.

We describe the effect of nonmagnetic impurity on the superconductivity behavior of the NdFeAsO0.8F0.2 iron-based superconductor. The resistivity measurements show that the superconductivity is suppressed upon increasing the low amounts of calcium impurity (x ≤ 0.05). Also, the TC decreases with the increase in the residual resistivity. Such behavior is qualitatively described by the Abrikosov–Gorkov theory and confirms that these impurities act as scattering centers. Moreover, we present the phase diagram of our synthesized samples for the various calcium dopings. We find that according to the increase in the calcium impurities and the decrease in the spin-density wave transition tempeθrature (TSDW), Fe ions are arranged stripe-antiferromagnetic at lower temperatures and also the superconducting transition temperature (TC) declines. Based on our results and in agreement with the available theories as is explained in the text, since the S++ state has no effect on the impurity-doped samples, and for low amounts of calcium, the S± state that is attributed to the spin-fluctuations causes the superconductivity suppression. So, it confirms the role of the spin-fluctuations as a dominant pairing mechanism in our synthesized samples.

The variations of superconducting and mechanical properties of La0.67Sr0.33MnO3 (LSMO) [x = 0.0, 0.1, and 0.2] doped YBa2Cu3O7−δ (YBCO) composite thick films were examined. All the composite films were synthesized by diffusion reaction technique. The structural and morphological analysis were investigated through X-ray powder diffraction along with Rietveld refinement and Field emission scanning electron microscopy (FESEM) respectively. The transport measurement suggested that the inclusion of ferromagnetic LSMO decreases the superconducting transition temperature ( $$ T_{C}^{on} $$ ) and enhances the residual resistivity (ρ0). The broadening of resistive transition occurs below the onset transition temperature and shows the dissipative flux pinning. Various superconducting parameters were obtained from the excess conductivity analysis of the composite films and were in good agreement with the experimental findings. The mechanical strength of all the composite films was explained through different models like Hays–Kendall model, Elastic/Plastic deformation model and Proportional specimen resistance model.

In this paper, the results of the superconductivity evaluation of MgB2 intermetallic-based superconducting materials prepared through mechanical alloying are reported. The formation of the MgB2 intermetallic phase took place through an intermediate phase reaction at the solid-state reaction temperature, which tends to favor single-phase materials. The annealing of mechanically milled Mg and B powders resulted in the highest mass fraction of MgB2 observed in this study, reaching more than 90% after annealing at 900 °C for 1 h. At that point, there were still second phases present consisting of Mg, MgO, and Fe2B. Improved superconducting properties were obtained in samples sintered at temperatures of 850 °C and 900 °C that had a low resistivity, low critical temperature gap values, and a high residual resistivity ratio (RRR).

We study the effect of addition of Ag on normal, paracoherent and superconducting coherent state of YBa2Cu3O7-δ (YBCO). We find that both room temperature resistivity and residual resistivity decrease with the addition of Ag in YBCO. In absence of magnetic field, the addition of Ag in YBCO shift various crossover temperatures of paracoherent state and 3D fluctuations dominate the mean-field region. However, the paracoherent state remains nearly unaffected in presence of 12 T magnetic field and 2D superconducting fluctuations dominate the mean-field region. The coherent state of YBCO improves by the addition of Ag in absence as well as in presence of 12 T magnetic field.

The Advanced Technology Centre (ATC) of National Astronomical Observatory of Japan is developing microwave kinetic inductance detectors (MKIDs) for large-array pixel cameras for millimeter and sub-millimeter astronomy. We investigated single-crystal Nb thin layers to form superconducting microresonators. We compared the performances of MKIDs based on crystalline Nb structure and those based on polycrystalline Nb. We carried out the entire manufacture of the detectors in the ATC clean room. DC magnetron sputtering is used to grow single-crystal Nb films on r-plane sapphire substrates at an elevated temperature of 800 °C. The residual resistivity ratio (RRR) measured on these single-crystal Nb layers reached values ranging from 40 to 80. We made MKIDs with this crystalline Nb layer, and we measured internal quality factors of the detectors up to 106. The measurement of the noise power spectral density of these MKIDs gave a low value of − 95 dBc/Hz from 100 Hz to 100 kHz. The internal quality factor Qi and the fractional resonance frequency change δfr/fr of MKIDs with respect to the temperature variation are usually following the extended Mattis–Bardeen equations. However, we noticed a deviation from the theoretical prediction for temperature lower than 1 K (in our case). This deviation has already been observed on Al MKIDs and explained by a theory taking into account the Kondo effect and the kinetic inductance contribution. We demonstrated that our measurements on single-crystal Nb MKIDs are also in agreement with the same theory.

Strength and electrical resistivity are coupled in metal alloys as both are based upon a similar microstructure mechanism, but the quantitative relationship between them is not known due to the complex microstructures involved. The present work analyzes the dependence of hardness and electrical resistivity on solute contents for ternary [Moy/(y+12)Ni12/(y+12)]xCu100−x alloys (at.%), where x = 0.3–15.0 is the total solute content and y = 0.5–6.0 the ratio between Mo and Ni. The alloys are designed following the cluster-plus-glue-atom model to reach three distinct structural states, i.e., cluster solution state (y = 1), where Mo is dissolved via a chemical short-range order characterized by Mo-centered and Ni-nearest-neighbored [Mo1-Ni12] cluster, cluster solution state plus extra Ni solution (y 1). The measured electrical resistivity and microhardness data are correlated with these three structural states to reveal the property dependencies on solute contents. The cluster solution enhances the strength, without causing much increase in the electrical resistivity, as the solutes are organized into cluster-type local atomic aggregates that decrease dislocation mobility more strongly than electron scattering. Analogous to residual resistivity ρR, which indicates the change of resistivity with reference to pure Cu, residual microhardness HR and residual lattice constant aR are also defined. For the ideal cluster solution state (y = 1, Mo/Ni = 1/12), the mentioned three parameters are correlated with the total solute content x by ρR = 1.08·x (10−8 Ω m), HR = 1.50·x (Kgf mm−2), and aR = − 1.08·x (10−4 nm). From these, ρR = 0.72HR = − aR. Such simple relationships indicate that resistivity and strength are dependent on the same cluster-type solution mechanism and can be a good reference for evaluating strength and resistivity performance of Cu alloys.

Monitoring and delineating the spatial distribution of shale fracturing is fundamentally important to shale gas production. Standard monitoring methods, such as time-lapse seismic, cross-well seismic and micro-seismic methods, are expensive, timeconsuming, and do not show the changes in the formation with time. The resistivities of hydraulic fracturing fluid and reservoir rocks were measured. The results suggest that the injection fluid and consequently the injected reservoir are characterized by very low resistivity and high chargeability. This allows using of the controlled-source electromagnetic method (CSEM) to monitor shale gas hydraulic fracturing. Based on the geoelectrical model which was proposed according to the well-log and seismic data in the test area the change rule of the reacted electrical field was studied to account for the change of shale resistivity, and then the normalized residual resistivity method for time lapse processing was given. The time-domain electromagnetic method (TDEM) was used to continuously monitor the shale gas fracturing at the Fulin shale gas field in southern China. A high-power transmitter and multi-channel transient electromagnetic receiver array were adopted. 9 h time series of Ex component of 224 sites which were laid out on the surface and over three fracturing stages of a horizontal well at 2800 m depth was recorded. After data processing and calculation of the normalized resistivity residuals, the changes in the Ex signal were determined and a dynamic 3D image of the change in resistivity was constructed. This allows modeling the spatial distribution of the fracturing fluid. The model results suggest that TDEM is promising for monitoring hydraulic fracturing of shale.

Potassium tungsten bronzes $$\hbox {K}_{x}\hbox {WO}_{3}$$ ( $$x=0.20$$ and 0.22) with the coexistence of charge density wave (CDW) and superconductivity (SC) were prepared from $$\hbox {K}_{2}\hbox {WO}_{4},\, \hbox {WO}_{3}$$ and W powders using a hybrid microwave method. The structure refinement confirmed that all samples had a pure hexagonal phase with the space group of $$P6_{3}$$ /mcm. The distortion degree of W–O octahedron declines with x and is independent of synthesis condition for the same x (=0.20). The CDW transition is studied as a function of residual resistivity ratio. By increasing the crystallinity of sample, this transition can be suppressed, which is probably attributed to the interaction between CDW and defects in crystallites. The CDW transition temperature increases with x, which may be related to the decline of the distortion degree of W–O octahedron. The competition between CDW and SC is observed according to the resistivity and magnetization measurements.

In the spin-valve Co/Pt/[Co/Pt]2 multilayers with perpendicular magnetic anisotropy, it has been found that magnetoresistance, anomalous Hall resistivity, and longitudinal resistivity demonstrate oscillatory behaviors with the increase in Pt spacer thickness. Moreover, the parameter b oscillates as a function of Pt spacer thickness, which is experimentally determined by fitting the equation $\rho _{AH} =a^{\prime }\rho _{xx0} +b\rho _{xx}^{2} $ (ρ x x0 is the residual resistivity, a ′ is the skew scattering parameter, and b consists of the side jump and the intrinsic contributions) via the temperature dependence of the resistivity. These observed oscillatory behaviors can be mainly ascribed to the polarization of Pt spacer, while the polarization in the Co/Pt multilayers depends on the Pt spacer thickness.

In this study, the magnetotransport measurements are performed in the field range of 0–7 T to determine the effect of Nd nanoparticles inserted in the Y-123 crystal structure on the superconducting characteristics and flux pinning mechanism of the YBa2−yNdyCu3O7 materials (0.000 ≤ y ≤ 0.500). Moreover, the experimental measurement results enable us to evaluate the crucial parameters as regards critical transition temperatures ( $$T_{c}^{onset}$$ and $$T_{c}^{offset}$$ ), room temperature resistivities (ρ300), residual resistivity ratios (RRR), thermodynamic critical fields (μ0Hc), lower critical fields (μ0Hc1), upper critical fields (μ0Hc2), critical fields (μ0Hc3), irreversibility fields (μ0Hirr), coherence lengths (ξ), penetration depths (λ) and Ginzburg–Landau ( $$\kappa$$ ) parameters. All the values obtained show the considerable improvement with the increment of the Nd nanoparticles in the Y-123 crystal system up to the critical value of y = 0.250 beyond which the prompt degradation begins in the crystal structure due to new induced artificial dislocations and permanent disorders in the Cu–O2 consecutively stacked layers. Hence, the excess Nd inclusions lead to the thermal motion of the vortices easily. This fact is completely confirmed by the magnetotransport measurements performed in the external magnetic fields. Namely, the optimum level of Nd dopant seriously increases the coupled regions as a result of the degradation of pancake positional fluctuations, and pinning of two-dimensional pancake vortices enhances with the recoupling of the adjacent layers. However in case of the maximum Nd inclusions, the flattened pancakes with more interplane interaction energy never travel from layer to layer due to the alteration of the coupled vortices into the discrete pancakelike (recoupling linelike) nature. In other words, the excess Nd nanoparticles inserted in the Y-123 crystal system reduce significantly the interlayer Josephson coupling length, elastic moduli of the vortex lattice and magnetic field carrying capacity. Furthermore, the flux pinning energy (U0) is calculated from thermally activated flux flow model. The activation energy computed increases regularly with the increment of Nd decorations until y = 0.250 after which the value significantly decreases towards to the global minimum point. However, the pinning energy values always decrease with the increase of the external magnetic field strength. In case of external magnetic fields of 7 T the maximum activation energy is found to be about 477 K. As for the Y-123 material doped with maximum Nd additives of y = 0.500, the flux pinning energy values are not calculated at any applied magnetic field which is >0.1 T due to the cooper pair-breaking in Ba-site Nd substituted Y-123 systems. At the same time, the evaluated parameters follow the same trend: firstly enhancement up to the critical Nd dopant value of y = 0.250 and then the rapid regression towards the global minimum point. Finally, the optimum Nd impurity level is found to be y = 0.250 in the Y-123 system at even higher applied magnetic field strengths.

CRESST-II is a direct dark matter experiment that uses scintillating calorimeters to detect WIMP-induced nuclear scatter processes. Heat and light signals are read out with tungsten transition edge sensors (TESs) that are optimized toward their sensitivity to non-thermal phonons. The usage of superconducting thin film structures (e.g., aluminum) serving as phonon collectors to increase the collection area for this signal component is an approach to improve the sensitivity of the TES. The performance of the phonon collectors depends on the material properties and the quality achieved in the production process. We optimized the size of the phonon collectors for the given quality of CRESST-II light detectors. The diffusion lengths measured in this work are $$\mathcal {O}$$ (1 mm) and show a strong correlation to the Residual Resistivity Ratio of the respective films. First tests of CRESST-II light detectors with larger as well as thicker phonon collectors individually show improvements in the measured pulse height of 30 %.

In the present paper, the formulae are summarized for the evaluation of magnetoresistance data from the measured field dependence of the resistivity obtained on thin strip-shaped samples of ferromagnetic metals and alloys with a finite residual resistivity for various relative orientations of the magnetic field and the measuring current. This sample shape simplifies the problem in that the specimen shape can be approximated with a general ellipsoid for which the demagnetizing fields can be estimated with sufficient accuracy from tabulated data. First, the various experimental configurations are defined for the magnetotransport measurements. Then, the formulae for describing the field-dependence of the resistivity in metallic ferromagnets with finite residual resistivity are discussed, by treating separately the case of low and high temperatures, low and high being defined with respect to the Curie temperature of the ferromagnet under study. The extraction of some magnetotransport parameters (anisotropic magnetoresistance and Hall effect) often requires an extrapolation of the measured data to zero magnetic field or zero magnetic induction and this will also be discussed. Finally, a summary of the relations between the experimentally measured magnetotransport parameters and those derived from theoretical calculations will be given.

Electrical resistivity measurement is an exact way to find defects in metals and alloys. Defects contribute to the residual resistivity, and determining their number is very important. Defining the inner electrical structure of an alloy is difficult, and especially it is unpredictable in alloys. This article offers a genetic programming formulation to learn how deposition conditions and alloy constituents affect the electrical resistivity of Cu–Zn alloy. Input parameters selected were: measurement temperature (K), Cu and Zn% content in the deposition bath and thin films, bath temperature, deposition potential, and the grain size of the samples. Electrical resistivity values were the output parameters. A total of 130 training and testing sets were selected. The comparative results prove the superior performance in predicting electrical resistivity of the films. The produced model proposes a close relationship for all the input parameters with the electrical resistivity property.

The various Co2MnSi films, from chemical ordered L21 state to completely disordered amorphous state, were prepared on glass substrates with different deposition/annealing temperatures. The influence of deposition/annealing temperature on the crystallographic defects and atomic disorders, and further on the magnetic and transport properties of the Co2MnSi films were investigated in detail. The decrease in crystallinity leads to the structure disorder, spin disorder and further the reduction of magnetization as well as the increase of residual resistivity. The dominant source in anomalous Hall effect for the polycrystalline samples is the skew scattering, while the skew scattering coefficient a becomes larger with the increasing deposition temperature, due to the increase of skew scattering center introduced by the increasing structure disorder.

In various \(\mathrm{FeTe}_{1-x}\mathrm{Se}_{\mathrm{x}}\) (x=0–1), members of the 11-iron-pnictide superconductor family, the temperature dependent resistivity ρ can be scaled into a universal curve. It is found that the ρ(T) dependences can be reproduced by the expressions \(\rho(T) = \rho_{0} - (c/T)\exp( - \frac{2\varDelta }{T})\) and \(\rho(T) =\rho_{0} + (c/T)\exp( - \frac{2\varDelta }{T})\) for x=0–0.3 and 0.4–1.0, respectively. The scaling was performed using the energy scale 2Δ, the parameter c, and the residual resistivity ρ0 as scaling parameters. The compositional variation of the scaling parameters 2Δ and ρ0 has been determined. The existence of a universal metallic ρ(T) curve is interpreted as an indication of a single mechanism which dominates the scattering of the charge carriers in FeTe1−xSex (x=0–1). Thus, the scaling of the normal-state properties seems to be a general feature not only for high-Tc cuprates but also for the iron-pnictides superconductor family.

We present a systematic study of the impurity scattering effect induced by Pd dopants in the superconductor SrPt3P. Using a solid-state reaction method, we fabricated the Pd-doped superconductor Sr(Pt1−x Pd x )3P.We found that the residual resistivity ρ 0 increases quickly with Pd doping, whereas the residual resistance ratio (RRR) displays a dramatic reduction. In addition, both the nonlinear field-dependent behavior of the Hall resistivity ρ xy and the strong temperature dependence of the Hall coefficient R H at low temperature are suppressed by Pd doping. All the experimental results can be explained by an increase in scattering by impurities induced by doping. Our results suggest that the Pt position is very crucial to the carrier conduction in the present system.

In this work, a series of ceramic samples of Bi1.6Pb0.4Sr2Ca2Cu3O y (Bi(Pb)-2223) added with different amounts (0, 0.2 and 0.4 wt%) of carbon nano-tubes (CNT) are prepared from commercial powders and characterized. The study shows that the volume fraction of the Bi(Pb)-2223 phase decreases with CNT content while the grain size of the samples increases. The obtained cell parameters as well as the onset critical transition temperature are independent of this kind of addition. Also, it has been concluded that CNT addition makes the grains of the samples more connected. The measured magnetization in FC and ZFC modes indicates that CNT addition makes the grains of the samples more connected even if the irreversibility line is decreased. The variation of the residual resistivity and metalicity with CNT content suggests that the addition introduces disorder and defects into the samples. Also, the added samples present broad transitions to the superconducting state when compared to the pure one; this result may be associated to the increase of the volume fraction of the secondary phases. The activation energies, upper critical fields H c2(0) and coherence lengths ξ(0) are extracted from the magneto-resistivity curves and their evolutions with CNT content are discussed.

The transport properties of Pd-rich PdFe alloys are investigated as a function of the atomic and magnetic orders on the L21 (Cu3Au) lattice. The residual resistivity, anisotropic magnetoresistance (AMR), and anomalous Hall effect are calculated from first-principles as a function of the atomic order. The calculations are based on the relativistic generalization of the transport Kubo–Greenwood approach as formulated in the framework of the first principles TB-LMTO method and Coherent Potential Approximation (CPA). The effect of the thermal magnetic disorder on the resistivity and AMR has been also studied using the disordered local moment approach based on the CPA. Our results are in an overall good agreement with available experimental data.

In the present work, lanthanum nickel oxide (LNO) thin films were prepared by the sol-gel method. Microstructures of the films were tailored by changing sol concentration so as to investigate the effect of grain boundary on the transport properties of electrons in the polycrystalline LNO films. Based on the temperature dependence of the resistivity and the magnetic field dependence of the magnetoresistance (MR) at various temperatures, the factors that dominate the transport behavior in the polycrystalline LNO films were explored in terms of weak localization and strong localization. The results show that the grain boundary has a significant influence on the transport behavior of the electrons in LNO films at a low-temperature region, which can be captured by a variable-range hopping (VRH) model. The increase of metal–insulator (M–I) transition temperature is ascribed to Anderson localization in grain boundary. At a high-temperature region, electron–electron scattering and electron–phonon scattering predominates in the films. In this case, the existence of more grain boundary shows a minor effect on the transport behavior of the electrons but elevates the residual resistivity of the films.

This study reports the role of various annealing time such as 0.5, 1, 1.5 and 2 h on the flux pinning mechanism, physical and superconducting properties of Cu-diffused bulk MgB2 superconductors prepared at 850 °C with the aid of the magnetoresistivity measurements performed in the magnetic filed range from 0 to 7 T. The critical transition (both \( T_{c}^{onset} \) and \( T_{c}^{offset} \)) temperatures, irreversibility fields (μ0Hirr), upper critical fields (μ0Hc2), residual resistivity ratios (RR), cross-sectional area fractions (AF), penetration depths (λ), coherence lengths (ξ) and electronic mean free paths (\( \ell \)) of the MgB2 materials are derived from the magnetoresistivity curves. At the same time, activation energy (U0) values are determined from thermally activated flux creep model. Furthermore, resistivity criteria of 10 and 90 % normal-state resistivity serve as the important parameters for the description of μ0Hirr and μ0Hc2 values, respectively. At absolute zero temperature (T = 0 K), the extrapolation of the μ0Hirr(T) and μ0Hc2(T) curves gives the μ0Hirr(0) and μ0Hc2(0) values of the samples prepared. Similarly, the ξ values are derived from the μ0Hc2(0) values when the λ values are deduced from the Ginzburg–Landau parameter (\( \kappa \)). It is noted that the pinning mechanism, physical and superconducting properties of the samples improve with the enhancement of the diffusion-annealing time up to 1 h beyond which these properties start to destroy systematically and in fact reach the local minimum point for the sample annealed at 850 °C for 2 h as a consequence of the degradation of pinning ability, density, crystallinity and connectivity between grains. Additionally, the presence of the magnetic field leads to reduce these properties due to the decrement of the flux pinning in the samples. Namely, the maximum \( T_{c}^{onset} \) and \( T_{c}^{offset} \) values are found to be about 39.3 and 38.3 K for the sample annealed at 850 °C for 1 h. With the increment in the applied magnetic field up to 7 T, these values decrease to 32.0 and 29.2 K, respectively. Likewise, the U0 value of the sample reduces from 9,162 to 2,968 K with the increase of the applied field. On the other hand, the minimum \( T_{c}^{onset} \) of 30.9 K, \( T_{c}^{offset} \) of 27.4 and U0 of 898 K at 7 T applied magnetic field are obtained for the sample annealed at 850 °C for 2 h, pointing out that the latter sample obtains much weaker flux pinning, lesser crystallinity and connectivity between grains compared to the other samples. The dissipation mechanism is also discussed from the results of the magnetic field and temperature dependence of the activation (flux pinning) energy.

This study manifests the change of the pinning mechanism, superconducting and physical properties of Cu-diffused MgB2 superconductors prepared at different annealing temperature from 650 to 850 °C by means of the magnetoresistivity measurements conducted at several applied magnetic fields in a range of 0–7 T as a function of temperature from 15 to 50 K. The onset (T c onset ) and offset (T c offset ) critical temperatures, activation energies (U0), irreversibility fields (μ0Hirr), upper critical fields (μ0Hc2), residual resistivity ratios (RR), cross-sectional area fractions (AF), penetration depths (λ), coherence lengths (ξ) and electronic mean free path ( $$ \ell $$ ) of the samples are evaluated from the magnetoresistivity curves. Thermally activated flux creep (TAFC) model is used for the determination of the U0 values; likewise, the μ0Hirr and μ0Hc2 values are obtained by resistivity criteria of 10 and 90 % normal-state resistivity, respectively. At absolute zero temperature (T = 0 K), the extrapolation of the μ0Hirr(T) and μ0Hc2(T) curves is used to find the μ0Hirr(0) and μ0Hc2(0) values of the samples. Moreover, the ξ values are deduced from the μ0Hc2(0) values when the λ values are calculated from the Ginzburg–Landau parameter ( $$ \kappa $$ ). It is found that the superconducting and physical properties of the samples improve with the increment of the diffusion-annealing temperature; however, the presence of the magnetic field leading to the decrease of the flux pinning in the samples causes the reduction of these properties. Namely, the T c onset and T c offset values are found to increase from 38.4 to 39.3 K and 36.9 and 38.3 K with the enhancement in the diffusion-annealing temperature at zero filed. Similarly, the U0 values increase significantly with the increase of the annealing temperature. In fact, the U0 of 9,162 K belonging to the sample annealed at 850 °C is determined to be the maximum activation energy value. On the other hand, the minimum T c onset of 30.9 K, T c offset of 27.6 K and U0 of 1,365 K at 7 T applied magnetic field are obtained for the pure sample, indicating that the sample annealed at 850 °C obtains much stronger flux pinning, better crystallinity and connectivity between grains compared to the other samples prepared. Based on these results, the superconducting and physical properties of the MgB2 superconductors produced in this work are observed to enhance with the increase of the diffusion-annealing temperature as a result of the improvement of pinning abilities, crystallinity and connectivity between grains. The magnetic field and temperature dependence of the activation energy are also discussed.

This report describes synthesis of binary Bi2Te3 and ternary Bi0.5Sb1.5Te3 single crystals using the halide chemical vapor transport technique. For synthesis of ternary Bi0.5Sb1.5Te3, BiBr3 is a more effective transport agent compared with iodine I2. The single crystal includes a few atomic percent of Br. The Bi0.5Sb1.5Te3 crystal shows p-type conduction and has a comparatively large residual resistivity ratio. The crystal exhibits relatively high electrical resistivity and high Seebeck coefficient. These high values are attributed to decrease of the hole concentration p due to doping of the transport agent Br.

We show that the temperature-dependent resistivity ρ(T), Hall number n H(T) and the cotangent of the Hall angle cot θ H(T) of Ba(Fe1−x Co x )As2 (x=0.0–0.2) can be scaled using a recently proposed model-independent scaling method (Luo et al. in Phys. Rev. B 77:014529, 2008). The zero field normal-state resistivity above T c can be reproduced by the expresion $\rho(T) = \rho_{0} +cT\exp(- \frac{2\varDelta }{T} )$ and scaled using the energy scale Δ, c and the residual resistivity ρ 0 as scaling parameters. The scaling parameters have been calculated and the compositional variation of 2Δ and ρ 0 has been determined. The 2Δ(x) dependence show almost linear decreasing in underdoped regime, minimum corresponding to the T c maximum and increasing in overdoped regime. The latter is different from that reported for cuprates. The existence of a universal metallic ρ(T) curve which, however, is restricted for the underdoped compounds to temperatures above a structural and antiferromagnetic transition is interpreted as an indication of a single mechanism which dominates the scattering of the charge carriers in Ba(Fe1−x Co x )As2 (x=0.0–0.2).

The variation of the normal phase resistance, transition width and critical temperature Tc by the irradiation bulk samples of Y123 with different doses of neutrons at the temperature range of 70

Measurements of microwave attenuation at room temperature and 4.2 K have been performed on some conductors commonly used in receiver input circuits. The reduction in loss on cooling is substantial, particularly for copper and plated gold, both of which showed a factor of 3 loss reduction. Copper passivated with benzotriazole shows the same loss as without passivation. The residual resistivity ratio between room temperature and 4.2 K, deduced from the measurements using the classical skin effect formula, was smaller than the measured DC value to a degree consistent with conduction in the extreme anomalous skin effect regime at cryogenic temperatures. The measurements were made in the 5-10 GHz range. The materials tested were: aluminum alloys 1100-T6 and 6061-O, C101 copper, benzotriazole treated C101 copper, and brass plated with electroformed copper, Pur-A-Gold 125-Au soft gold, and BDT200 bright gold., Comment: 9 pages

High-purity high residual resistivity ratio niobium is used to fabricate particle accelerator cavities for advanced superconducting accelerators. This material has an unstable texture that causes different r values in different inplane directions, which evolve with deformation, making prediction of forming characteristics difficult. Thus, an evolutionary yield function having coefficients that evolve with plastic deformation is introduced to account for gradients in microstructure and texture that evolve differently in different layers of the material. With such a model, failure modes and locations are predicted accurately in more complex deformation conditions.

We are developing transition edge sensors (TES) using single layer iridium (Ir) as the detector and deposited tin (Sn) as the absorber. We obtained good Ir devices with reproducible and uniform transition temperature around 120 mK, transition widths of 1–2 mK, residual resistivity ratio (RRR) between 1.8–3 and high sensitivity α. Our Ir films are obtained using radio frequency (RF) magnetron sputtering and photolithography. In this paper we present a full low temperature characterization of the Ir films.

Common and distinctive features of the temperature dependences of microwave surface impedance Z(T) = R(T) + iX(T) and conductivity σ(T )i n theab-plane and along the c-axis of high-Tc single crystals (HTSC) are discussed. The main attention is focused on an evo- lution of these dependences in YBaCuO crystal with the oxygen deficiency. Comparison of YBaCuO with other HTSC crystals reveals a number of peculiarities, namely, the linear de- pendence Rab(T) ∝ T up to Tc/2 in HTSC single crystals with tetragonal lattice and up to Tc/3 in YBaCuO where Rab(T) shows also a broad peak at T ∼ Tc/2; breakdown of normal skin effect in some HTSC crystals; dramatic effect of pseudogap on the superfluid density in the heavily underdoped YBCO; several orders of magnitude higher residual surface resistance in HTSC when compared to conventional superconductors; etc. Possible explanations are discussed in the context of the specific features of HTSC structure and in the framework of recent models of quasiparticles' c-transport and pseudogap state in HTSC.

The three dimensional (3D) Dirac semimetal is a new quantum state of matter that has attracted much attention recently in physics and material science. Here, we report on the growth of large plate-like single crystals of Cd3As2 in two major orientations by a self-selecting vapor growth (SSVG) method and the optimum growth conditions have been experimentally determined. The crystalline imperfections and electrical properties of the crystals were examined with transmission electron microscopy (TEM), scanning tunneling microscopy (STM) and transport property measurements. This SSVG method makes it possible to control the as-grown crystal compositions with excess Cd or As leading to mobilities near 5–105 cm2V−1s−1. Zn-doping can effectively reduce the carrier density to reach the maximum residual resistivity ratio (RRR"Equation missing"ρ300K/ρ5K) of 7.6. A vacuum-cleaved single crystal has been investigated using angle-resolved photoemission spectroscopy (ARPES) to reveal a single Dirac cone near the center of the surface Brillouin zone with a binding energy of approximately 200 meV.

WOS: 000239637700020, Cd-Sn, Bi-Cd, and Al-Si eutectic and Al-3wt.%Si hypoeutectic alloys of high-purity (99.99%) metals were produced in a vacuum atmosphere. Current-voltage (I-V) characteristics of these specimens were measured at various temperatures between 100 and 475 K. The electrical resistivity (p) and temperature coefficient (alpha) for each specimen, depending on the temperature, were calculated using results obtained from the I-V measurements. The electrical resistivities and the residual resistivity of the specimens increase with increasing temperature for each alloy system. These results are compared with literature results.

Polycrystalline Au films with thicknesses between 30 nm and 80 nm were stepwise implanted with Fe+ ions at liquid helium temperature up to a concentration of 130 ppm and the resulting Kondo behavior was determined in situ down to 1.4 K applying an ac-technique with a resistance resolution of 2×10-5. Combining the implantation with various annealing steps as well as further Ar+ ion irradiations, the degree of disorder within the samples could be systematically varied. From the results, it is concluded that different types of defects must be distinguished when discussing the effect of disorder on the Kondo behavior: Defects which are closely trapped by the Fe atoms and strongly influence the Kondo effect, while hardly affecting the value of the residual resistivity, and defects which are sufficiently far away from the Fe atoms to exclude any direct influence. This second type strongly contributes to the residual resistivity without a correspondingly large effect on the Kondo behavior.

The paper shows that high-quality super-conducting Nb films can be deposited by means of arc discharges under ultra-high vacuum conditions. The critical temperatureT c of Nb-films obtained with a planar cathodic arc Ultra High Vacuum (UHV) system, is very close to that of pure bulk niobiumT c=9.26 K and the transition to super-conducting state is very narrow. The films have higher Residual Resistivity Ratio (RRR) values (up to 80) and larger grain sizes, as compared with sputtered Nb-films deposited at the same temperature.

We have studied the effect of Zn substitution on the temperature dependence of the resistivity and the Curie temperature T p of La1−x Ca x Mn1−y Zn y O3 system (with x=0, y=0, and x=0.33, 0.00≤y≤0.15) during their pass to the paramagnetic conducting phase. All the specimens show a clear metal-insulator transition passing through the Curie temperature T p . With increasing Zn concentration, T p decreases for La/Ca substitution and also for Zn/Mn substitution with fixed 33 at.% of Ca. T p is found to be slightly decreases for low concentrations of Zn (up to y=0.075) followed by a sharp decrease up to y=0.15. A possible explanation is given. Moreover, the activation energy E a is calculated in the three different temperature regions characterized in the (ρ-T) curve. Decreasing the temperature below T p can increase the parallel alignment of the Mn spins and, thus decreases the resistivity of the samples. E a increases with Zn content (up to y=0.075) followed by a sharp decrease. A strong correlation in the behavior of the normal state and residual resistivity as well as T p and E a with Zn content is reported.

The magnetoresistivity of tungsten single crystals with a residual resistivity ratio of up to 70,000 was measured in the temperature range from 4.2 to 55 K in a magnetic field of 10 T. The size effect, i.e., the linear dependence of the magnetoconductivity on the inverse sample dimensions, has been observed in the high-field magnetoconductivity. The experiments show that this phenomenon can be used to separate and study the surface and volume contributions to the magnetoresistivity of pure single crystals of compensated metals from liquid helium temperature up to approximately 25 K. It is shown that the specular reflection coefficient of the conduction electrons for pure metals in high magnetic fields can be determined in this way.

Co2MnGa and Co2MnIn are ideal half-metallic materials for spin-injection in nanostructured semiconductor devices.Magneto-optical Kerr effect and electrical transport measurements demonstrate that although these alloys can be integrated with semiconductor devices, the metallic phase dominates over the intrinsic, minority spin phase of the alloy. Co2MnGa : GaAs(001) has a weak uniaxial magnetic anisotropy with the easy axis along the [0,−1,1] in-plane direction. Co2MnIn : GaAs(001) has no in-plane anisotropy. Metallic behavior is concomitant with ferromagnetic behavior, as the anisotropic magnetoresistance tends to zero at the same film thickness (∼100 A) that the residual resistivity ratio extrapolates to 1. Co2MnIn has an AMR of ∼0.5%, however, an AMR as large as 6% is observed in Co2MnGa at 300 K. This demonstrates the potential for nanostructured devices, although the first 100 A of alloy growth will determine the spin-injection efficiency.

Rh interacts with Hg to form stable intermediate phases. By combining data from several investigations, [1967Jan] constructed a phase diagram for pressures sufficiently high to retain Hg in condensed form. This diagram, with slight modification by the present author, is depicted in Fig. 1. The diagram in Fig. 2 is based on the same data and shows equilibria that would be expected at a pressure of 0.1013 MPa (1 atm). The invariant temperatures of both the higher pressure version and the ambient pressure version of Hg-Rh phase relationships are listed in Tables 1 and 2, respectively. These temperatures were estimated from the vapor pressure equations reported in [1967Jan] (for the equations, see Thermodynamics Section, Table 5); however, because of uncertainties in the logarithms of the vapor pressure data, the resultant invariant temperature values are unlikely to have precisions of better than 10%. Thus, the apparent inversions of the order between the decomposition temperatures of Hg5Rh and Hg4.63Rh in Fig. 1 and 2 may or may not be significant. Likewise, no difference between the melting points of pure Hg and Hg saturated with Rh is experimentally detectable; so whether the invariant equilibria between Hg and Hg5Rh is characterized by a peritectic or eutectic reaction is a meaningless discussion. An initial determination of Rh solubility in liquid Hg was made by [1956Str] by chemical analysis of the saturated filtrate. A value of 0.31 at.% Rh at room temperature was obtained. A later determination by [1973Jan1] reported a value of 1 × 10 at.% Rh at 500 °C. The determination again was made by analysis of the saturated filtrate, but the analysis was done spectroscopically after the Sn was added and then the Hg was evaporated. This latter analysis is believed to be more reliable than the former. [1971Ale] used residual resistivity measurements to estimate a value of

Electron-doped metallic states of Ca1−x Y x VO3 and Ca1−x Y x TiO3 change into non-metallic states around x∼0.4 and 0.6, respectively. The residual resistivity in the metallic states increases with increasing effective magnetic moment or coefficient of T 2 term of resistivity. The effective moment reaches ∼ 0.5 µB/molecule in Ca1−x Y x VO3 and also in Ca1−x Y x TiO3 near the metal-nonmetal phase boundary. In these metallic states. ∼ 10% of 3d atoms seem to have large localized magnetic moments. In electron-doped metallic sample of Ca1−x Y x VO3, the temperature dependence of resistance shows no resistance-minimum. However, weak negative magneto-resistance is observed for the sample with x=0.2 up to 50 Tesla at 4.2 K.

We have investigated the low temperature properties of the narrow-gap semiconductor SmB6 by means of electrical resistivity and specific heat measurements. Results imply that the residual resistivity below about 3 K is non-activated and the corresponding state, which is formed within the in-gap states, has a metallic-like nature. Heat capacity measurements confirmed the metallic-like properties of the in-gap states and revealed, moreover, an enhancement of the specific heat below 2 K which is more expressive for the sample with a lower amount of impurities. The observed behaviour can be attributed to the formation of a coherent state within the in-gap states of this compound.

The electronic structure and the residual resistivity of random FeRh-based alloys in the CsCl structure are calculated from first principles. The calculations are performed for different spin structures using the tight-binding linear muffin-tin orbital method in the atomic sphere approximation. The effect of late transition-metal impurities (Pd, Rh) is taken into account by means of the coherent potential approximation generalized to inhomogeneous systems. It is shown that impurity scattering leads to giant magnetoresistance effects in qualitative agreement with experiment.

Metals near quantum critical points have been predicted to display universal out-of equilibrium behavior in the steady current-carrying state. We have studied the non-linear conductivity of high-quality CaRuO$_3$ thin films with residual resistivity ratio up to 57 using micro-second short, high-field current pulses at low temperatures. Even for the shortest pulses of $5\mu$s, Joule heating persists, making it impossible to observe a possible universal non-linearity. Much shorter pulses are needed for the investigation of universal non-linear conductivity., Comment: 9 pages, 7 figures

We present a systematic investigation of conditions for heat treatment of Rh with the aim of increasing the residual resistivity ratio (RRR). The maximal value of RRR for a 25 μm thick foil was found to be 1050 and the optimal treatment conditions were high temperatures, above 1400°C, and a low pressure of pure oxygen, around 1 μbar. Another batch of foils, containing less magnetic impurities, showed an RRR of only 600. A 0.4 mm thick single crystal was heat treated to an RRR value of 740. Our findings are discussed in the light of a model with magnetic and non-magnetic impurities in Rh, where the latter is found to have an important contribution for this unusual metal. Especially carbon impurities were found to be quite detrimental for the resistivity, and the recovery of the RRR after a carbon contamination is extremely slow in subsequent heat treatments.

The temperature dependent surface impedance Zs(T) of single-crystalline YBa2Cu3O7-x (YBCO) was analyzed within the two-fluid model in terms of the fraction of paired charge carriers, fs(T), and of the quasiparticle scattering time. The usual approach was extended by considering a temperature dependent effective quasiparticle mass m*(T), which results from a strong electron-phonon interaction. This effect must not be neglected in the description of high-temperature superconductors due to the large ratio of Tc to the Debye temperature TD. The temperature dependence of the penetration depth, of high-quality YBCO crystals and films could be described with an electron-phonon coupling constant, and using fs(T) = 1- (T/Tc)2.8 as an approximation of the BCS theory. Different trial phonon spectra were encountered in terms of their ability to reproduce the -data. The scattering time was described by the Bloch-Gruneisen formalism with TD=460 K. Assuming an Einstein spectrum with, a residual resistivity and a fraction of unpaired quasiparticles at T = 0 K yielded a surprisingly good agreement of the model with Zs(T)-data measured at 87 GHz with a high-quality epitaxial YBCO film between T=4 K and Tc. While an exact reproduction of the surface impedance asks for a rigorous theoretical computation, our analysis demonstrates that strong electron-phonon coupling is relevant for discussing the unconventional transport properties of YBCO.

Sputter-quenched SiO2 films containing Pb, which is insoluble to SiO2, have been found to exhibit a remarkably enhanced upper critical field (Hc2), which is about 90 times higher than that of pure Pb The sputtered films consisted of an amorphous SiO2 matrix and fcc Pb particles, dispersed homogeneously in the amorphous matrix. The particle sizes and interparticle distances were about 5 to 350 nm and 5 to 50 nm, respectively The superconducting transition temperature (Tc), upper critical magnetic field (Hc2) at 4.2 K, and residual resistivity (p10) at 10 K were 7.05 K, 4.37 T and 1.4x102 μΩm for (SiO2)29Pb71(vol %), respectively Since thel eff evaluated from linearized Ginzburg-Landau equation was 0.524 nm for x=71%, while theof pure Pb at 4.2 K was valued at 2.3xl05 nm, it can be concluded that thel eff of these SiO2-Pb films was drastically reduced owing to the refinement of Pb particles and internal defects (stress) induced by vapor quenching. Therefore the high field superconductivity can be interpreted mainly due to the significant decrease of coherence length, resulting from the large reduction of the effective mean free path length (l eff) of electrons The dual phase microstructure also had influence on the increase of the fluxoid pinning force and behaved like a type-II superconductor

The superconducting properties of the heavy fermion UPt3have been changed by irradiation with high energy electrons which creates point defects in a reproducible and controled way. Measurements of the residual resistivity, critical temperature, upper critical field and thermal conductivity have been realized on these irradiated samples. The strong suppresion of superconductivity with increasing defect concentration is in agreement with the theory of unconventional superconductivity. However, our thermal conductivity data contradicts the simple predictions derived from the most popular modelsE1gand E2u) of the superconducting order parameter in UPt3.

Thin metallic films are required to provide interconnection between contacts on devices and between devices. As device dimensions decrease, the low electrical resistivity becomes the most important issue in microelectronics industry. Recently in thin metallic films, hydrogen has been shown to lower the electrical resistivity of thin metallic films, reduce the rate of electromigration in interconnect lines, and lower the stress generated in thin metallic films during annealing. These effects are referred to as hydrogen effects. Low temperature resistivity measurements were performed to determine the effect of hydrogen and temperature on the resistivity of an aluminum-2 wt % copper film. Low temperature control experiments were performed in helium since it has a similar thermal conductivity as hydrogen but is chemically inert . The electrical resistivity of an aluminum-2 wt % copper alloy is lowered by hydrogen even at low temperature. The temperature coefficient of resistivity (TCR) values are identical within the experimental error (±0.005 μΩ cm/K). This means that phonon scattering is identical. So the decrease of the electrical resistivity is due to the decrease in the residual resistivity. Hydrogen effects are reversible for an aluminum-2 wt % copper alloy at room temperature because the adsorption and desorption of hydrogen occur. Hydrogen effects are slowly reversible for an aluminum-2 wt % copper alloy at low temperature because the adsorption of hydrogen occurs, but the desorption of hydrogen does not occur readily.

The anion-disorder and two-dimensionality effect for the superconducting and SDW phase of (TMTSF){sub 2}ClO{sub 4} was investigated through static magnetization and resistance measurements for various cooling rates through the ClO{sub 4}{sup {minus}} anion ordering temperature. In the slowly cooled phase, the authors find a strong dependence of the superconducting transition temperature on the a-axis residual resistivity {rho}{sub a} due to the suppression of anion ordering. This behavior supports models of non-s-wave pairing in (TMTSF){sub 2}X. In the rapidly quenched phase, the transition temperature of SDW shows a large increase in the magnetic field. This means that the SDW phase of quenched (TMTSF){sub 2}ClO{sub 4} is strongly suppressed by the two-dimensionality of the system.

A geometric renormalization associated with microstructure in coalescing silver films is shown to be responsible for metallic behavior on anomalously high resistivity scales. The signature for this effect, a proportional enhancement of residual resistivity and the temperature slope, may help determine the relevance of microstructure to other “band metal” systems.