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BackgroundNovel Coronavirus pneumonia 2019 (COVID-19) is a systemic infectious disease with prominent involvement of the respiratory tract, due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)[1]. Systemic lupus erythematosus is charcterized by an aberrant immune response with the presence of circulating autoantibodies, lymphopenia, and proinflammatory[2]. They are immune-compromised and vulnerable to infections with immune-suppressants treatment. However, data regarding the impact of COVID-19 pandemic in patients with SLE and drug use were relatively scarce.ObjectivesThe prevalence of COVID-19 in SLE patients was estimated by means of meta-analysis, and the effect of the use of anti-rheumatic drugs on the clinical outcome of SLE patients with COVID-19 was investigated.MethodsCross-sectional investigations and case series on SLE and COVID-19 published by CBM, CNKI, China Science and Technology Journal Database, Wan Fang Data, PubMed, Embase, Web of Science, Cochrane Library and Medline from its establishment to November 10, 2021 were searched. Random effects model was used to pool data. Heterogeneity and risk of bias was examined with I-squared index (I2) statistic. Inconsistency was evaluated by using the I2. Egger tests were used for the evaluation of potential publication bias (STATA v.12.0).ResultsA total of 14 studies comprising 5365 patients were identified (Table 1). Overall prevalence of COVID-19 in SLE patients was 1.5% (95%CI: 1.2%-1.8%). Eight of the studies included patients who used hydroxychloroquine as part of their treatment regimen, with 29.8% (95%CI: 25.8%-33.8%) hospitalization rates and 14.6% (95%CI: 11.5%-17.8%) adverse outcome rates. Among patients treated with hydroxychloroquine throughout the course of disease, the prevalence was 0.7% (95%CI: 0.4%-1.0%, Figure 1).Table 1.Summary of study characteristics of included records.AuthorTotal number of patientsMean/Median AgeHCQOther therapeutic drugsNumber of COVID19(n)Mean/Median AgeHCQOther therapeutic drugsHospitalization(n)supplemental oxyge(n)Combined poor outcomesGerard Espinosa40050.7GCs:47447.922GCs:12,T-DMARD:28,others:13334Emanuele Bozzalla Cassione16552.5127T-DMARD:12,others:411252.53GCs:1,others:31Ren: Cordtz253355.41170GCs:685,B-DMARD:42,T-DMARD:374,others:9261669.15GCs:416Ruth Fernandez-Ruiz226834332GCs:18,T-DMARD:5,others:5024198Zos Gendebien22551.7152GCs:92,T-DMARD:25,others:523222Wendy Wan Hui Lee8538.2858GCs:54,others:502311Giuseppe A. Ramirez, MD417others:389,combination:2891411Samar Tharwat20030.1140GCs:174,B-DMARD:4,T-DMARD:310,others:18432Dina Zucchi33247267GCs:176,B-DMARD:41,T-DMARD:118,others:118,combination:112640.36GCs:6,T-DMARD:1,others:6311Sarthak Gupta177GCs:81746.11GCs:12,T-DMARD:31022Seow Lin Chuah181838uah67Claudia Diniz Lopes Marques11033445 (31ques118GCs:134,T-DMARD:110,others:2841103578Beth Wallace31616GCs:12,others:4554 (26-67)4GCs:4,others:355Isabela Maria Bertoglio38245.138245.5206173Figure 1.A:Forest map of a meta-analysis of COVID-19 prevalence in SLE patients.B: Forest map of a meta-analysis of hospitalization rates among patients treated with hydroxychloroquine.C:Forest map of meta-analysis of the rate of adverse outcomes in patients using hydroxychloroquine as part of a treatment regimen.D:Forest map of a meta-analysis of the prevalence of patients treated with hydroxychloroquine throughout the course.ConclusionPatients with SLE had a higher risk of COVID-19. Hydroxychloroquine might benefit to reduce the overall hospitalization rate and prevalence rate of COVID-19, and alleviate inflammatory damage in the chronic stage of viral infection by inhibiting over activation of the immune system.References[1]SCHULTZE J L, ASCHENBRENNER A C. COVID-19 and the human innate immune system [J]. Cell, 2021, 184(7): 1671-92.[2]KIRIAKIDOU M, CHING C L. Systemic Lupus Erythematosus [J]. Ann Intern Med, 2020, 172(11): Itc81-itc96.AcknowledgementsThis work was supported by the National Natural Science Foundation of China (No. 82001740).Disclosure of InterestsNone declared

Two kinds of alloy materials which own the different copper contents are studied in this paper. After heating treatment, quenching and tempering, the mechanical properties and electromagnetic properties of two materials are tested by experimental equipment. Based on electromagnetic field theory, two-dimensional mathematical and physical models of induction motor with compound cage rotor are established. The finite element method for solving sine variation field is given using the software ANSYS. The starting performance and operating performance are used in the rotor bar. The influence of copper content change in alloy material on performance of induction motor with compound cage rotor is analysed. The results show that starting performance is better when Fe–20%Cu alloy is used in the rotor bar and operating performance is better when Fe–16%Cu alloy is used in the rotor bar. Its validity was verified by measurements.

Flake graphite cast iron (FC) samples containing 2%Si, in which the S contents changed from 0˙006 to 0˙076%, were heated at 1123 to 1323 K and then cooled to determine the pearlite morphological change, namely lamellar or granular. For the spheroidal graphite cast iron (FCD) samples, the P contents changed from 0 to 0˙2% and those of Sn were from 0 to 0˙06% with 0˙5%Cu using the 2˙5%Si and 0˙3%Mn iron.The pearlite morphology of the FC samples cooled from 1123 K was granular. The pearlite structure of the Sn–FCD samples was also granular, when cooled from 973 and 1023 K, and that of P–FCD was granular only in the sample cooled from 1023 K, otherwise the morphology was lamellar.The pearlite morphology of FC and FCD samples depends on the solubility of C in the austenite which can be varied by the heating temperature. This mechanism is identical to that of the lamellar to rod transition in eutectic alloys.

The temperature dependence of the local structure of liquid Sb has been studied by x-ray absorption spectroscopy. It is shown that about 10% of the atoms with coordination of 3 and weak Peierls distortion exist in liquid Sb just above its melting point. The Peierls distortion weakens gradually with increasing temperature and vanishes at about 750 degrees C. This structural variation in liquid Sb is different from the normal liquid-liquid phase transition. This work reveals the relationship between the variation in the local structure and the change in the physical properties, such as the electrical resisitvity of liquid Sb, with temperature. The complete agreement between the measured electrical resistivity values during heating and cooling processes suggests that the structural units with the features of a rhombohedron appear above the melting point of Sb during solidification. (c) 2008 American Institute of Physics.

The heterostructure of Pt/Ba0.5Sr0.5TiO3/La0.67Sr0.33MnO3 (Pt/BST/LSMO) with the BST thickness ranging from 120 to 550 nm was fabricated by pulsed laser deposition. The dielectric constant (e) of the heterostructure was measured under different electrical fields (E) and frequency (f). A strong thickness dependence of the value of e, the e–E dependence and the e–f dependence were observed, which can be well explained by the series-capacitor model, based on the assumption that the heterostructure electrically consists of a 'bulk' layer and an interfacial layer between the Pt and BST layers. The dielectric properties of the 'bulk' layer and the interface layer were obtained. At room temperature, the dielectric constant of the 'bulk' layer was 1204 (at 100 kHz) and had a power law dependence on frequency. The ratio of thickness over the dielectric constant (di/ei) of the interface layer, which was used to characterize the property of the Pt/BST interface, was found to be around 0.08 nm at room temperature and to be independent of frequency.

Near-normal incident infrared reflectivity spectra of a (001) YVO4 single crystal have been measured at different temperatures in the frequency region between 100 and 6000 cm-1. The reflectivity spectra are analyzed with the factorized form of the dielectric function, and the dielectric properties and optical conductivity of the YVO4 crystal are obtained. From the TO/LO splitting, effective charges at different temperatures are calculated to study the ionicity of YVO4. The internal modes of the VO43- ion and the external modes of the Y(VO4) lattice are compared with SiO44- in zircon and with other rare-earth vanadates.

Near normal incident infrared reflectivity spectra of (001) SrTi1−xNbxO3 single crystal have been measured at different temperatures in the frequency region between 100 and 6000 cm−1. The optical parameters of phonons and plasmons are obtained on the basis of the double-damping extended Drude model. The lowest frequency phonon mode at 175 cm−1 softens with decreasing temperature, and the plasmon frequency triples when the temperature decreases from 300 to 10 K. Extra absorption near the highest frequency longitudinal phonon mode shows that the effect of the polarons should be taken into account in addition to the plasmon–phonon coupling. The splitting of the last high reflectivity band, the temperature dependence of the 615 cm−1 structure and the appearance of a new weak peak-like defect mode provide evidence for the existence of small polarons.

The microstructure of La0.7Sr0.3MnO3/Ba0.7Sr0.3TiO3/La0.7Sr0.3MnO3 (LSMO/BST/LSMO) thin films epitaxially grown on (0 0 1) SrTiO3 substrate by pulsed laser deposition was investigated by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Both threading dislocations (TDs) and misfit dislocations (MDs) were found in the films. Diffraction contrast and convergent beam electron diffraction (CBED) analyses reveal that the TDs are mostly pure-screw-type with Burgers vectors b = [001]. The MDs of edge character are located at both top LSMO/BST and bottom LSMO/BST interfaces with predominant [100] and [101] Burgers vectors. The average spacings between neighboring MDs at both LSMO/BST interfaces are smaller than that derived from lattice mismatch, which indicates the films are partly relaxed. (c) 2005 Elsevier B.V. All rights reserved.

Near-normal incidence infrared reflectivity spectra of (001) strontium lanthanum aluminate (SrLaAlO4) single crystal have been measured under different temperatures in the frequency region between 100 and 6500 cm−1. Five phonon modes are distinguished at low frequency while no spectral features were observed above 1000 cm−1. All the reflectivity spectra are fitted with the factorized form of the dielectric function. The dielectric properties of the SrLaAlO4 crystal in far-infrared region are presented and analyzed.

The effect of magnetic field and disorder on the transport properties of the underdoped Y0.5Pr0.5Ba2Cu3O7 − δ films has been investigated in a broad temperature range in magnetic fields up to 50 T. In ultrathin films with strong disorder, where the mean free path l corresponds to kFl 14 in normal state), the high magnetic field, by suppressing superconductivity, recovers the normal-state transport behavior with the ρab ~ ln {T}-dependence at low temperature in ~ 50 T field. The two different transport behaviors indicate that the normal-state transport properties of the underdoped cuprates are very sensitive not only to the hole concentration but also to the degree of the disorder.

Using numerical simulations we investigate the angular dependence of the vortex depinning transition at an incommensurate field above the first matching field in regular arrays of asymmetric pinning centers, modeled by the superposition of two interpenetrating square lattices of weak and strong pinning centers. The asymmetric pinning potentials can cause significant influence on the vortex motion when the vortices are driven at different angles with respect to the principle axes of the pinning lattice by the study of V – F L curves. We propose that the anisotropic critical driving force for the vortex motion will be modulated by both the shape of the individual pinning center and the periodic structure of the pinning lattice. Moreover, we find that the anisotropic depinning transition of the driven vortices is very sensitive to the shift between the two pinning sublattices.

A series of light oxygen doped Cu-rich La 2 CuO 4+δ samples, with δ < 0.01 and the nominal composition of cations being La:Cu=2:1 +x (0≤x≤0.18), have been investigated. Characterization shows that the samples are single phase till x ≥ 0.10. TEM, electron energy loss spectroscopy, magnetization and electric transport measurements show that the excess Cu (the substitution of Cu 2+ for La 3+ ) can enhance the 3D antiferromagnetic (AF) exchange interaction and promote electronic phase separation. In the AF background the hole-rich cluster caused by phase separation becomes superconducting below 34 K, and shows ferromagnetism from the superconducting transition temperature Tc to above the Neel temperature T N .

Bi2Sr2CaCu2O8+delta (Bi2212) single crystals embedded with MgO particles are successfully synthesized. The critical current density of Bi2212 single crystals with an appropriate amount of MgO doping is noticeably increased at low temperatures below 20 K with applied magnetic fields parallel to the c-axis as compared with undoped samples. Whereas at T greater than or equal to 25 K, there is no extra flux pinning in MgO-doped samples. Microstructure analyses reveal that MgO doping induces a high density of dislocations in the ab plane of Bi2212 matrix, which may be responsible for the enhanced flux pinning at low temperatures. (C) 2001 Elsevier Science B.V. All rights reserved.

The Cu-rich La2CuO4+delta ([La]:[Cu] = 2:1 + x) samples with 0 less than or equal to x less than or equal to 0.18 are characterized using X-ray diffraction, transmission electron microscopy and electron energy loss spectrum methods. The excess Cu is identified to occupy the La site and the maximum of such substitution, i.e., the maximum of excess Cu content, x, is examined to be about 0.06. From the magnetization measurements of the samples with different excess Cu, we find that the substitution of Cu for La can remarkably enhance the three-dimensional antiferromagnetic exchange interaction, thus, promoting electronic phase separation in La2CuO4+delta system with delta < 0.01. (C) 2001 Elsevier Science B.V. All rights reserved.

The techniques of transmission electron microscopy and electron energy loss spectroscopy (EELS) have been used for characterizing heavily Cu-doped polycrystalline La2CuO4.003 (LCO) samples. Semiquantitative and spatially resolved EELS analysis reveals that Cu may be doped into LCO lattice and that Cu doping introduces effectively holes into the sample. At room temperature, the LCO grains were found to phase separate into hole-poor and hole-rich grains, and in hole-rich grains holes were found to have a strong tendency to concentrate and form one-dimensional static ordering with planar domain wall promoted by high-energy electron beam. Two kinds of modulation vectors have been found, they are 1/4b* +/- 1/3c* (with a wavelength similar to 18.9 Angstrom) and 1/6a* +/- 1/3b* +/- 1/2c* (with a wavelength similar to 12.7 Angstrom). At lower temperatures, sharper and higher-order superlattice reflections were observed, indicating an enhanced charge ordering, and superlattice reflections originating from 1/4b* +/- 1/3c* were found to dominate those originating from 1/6a* +/- 1/3b* +/- 1/2c* with a shorter modulation period.

In this paper, we report tunneling spectroscopies on overdoped Bi 2 Sr 1.94 La 0.06 CuO 6+ δ (Bi2201) single crystals taken by point-contact with gold tips. Below the superconducting transition temperature, temperature-dependent Andreev reflection, zero bias conductance peak (ZBCP), a dip feature at |eV|∼2 Δ and the asymmetrical conductance curve have been observed. Quantitative analysis using extended BTK theory results in that d x 2 − y 2 and, in some cases, mixed order parameter symmetry can fit well to the experimental data. The fitted s -wave component is varied for different run experiments even with the same crystal, indicating that it is determined by the detailed contact condition between tip and crystal. The observed temperature ( T ) dependence of the energy gap deviates from the BCS-type. A dip feature at |eV|∼2 Δ scales with Δ for T below T c , revealing it may relate to the pairing interaction in the high T c superconductor.

Very smooth epitaxial Pb(Zr0.53Ti0.47)O3/YBa2Cu3O7-δ heterostructures have been fabricated on (100) SrTiO3 substrates by magnetron sputtering. The smooth YBCO (yttrium-barium-copper oxide) bottom layer is a-axis oriented, with low roughness of ~1.7 nm in a randomly selected 10 µm×10 µm area. Highly c-axis-oriented PZT (Pb(Zr, Ti)O3) films were grown on the YBCO layer, with average roughness of ~1.6 nm. However, when the deposition temperature is increased, the grain size of the PZT films increases from ~0.1 µm to ~0.3 µm, and the roughness increases too. Large-area ferroelectricity was investigated for such heterostructures, and it is found that as the deposition temperature was increased, both the saturation polarization and the depolarization were enhanced, while the remanent polarization and coercive field were decreased. Further study on the depolarization induced by interfacial effects was carried out as well.

Sn(1-x)Mn(x)O(2) (x

The structures of Pb ( Zr x Ti 1-x) O 3/ YBCO heterostructure with different thickness of PZT sublayer were investigated. The lattice parameter, c of YBCO layer is obtained to be c=11.686±0.001 Å, being of 0.2% larger than that of the bulk one. The lattice parameter, c of PZT layer is c=4.116±0.001 Å, indicating that the composition of the sample is Pb ( Zr 0.48 Ti 0.52) O 3. The misorientations of YBCO/PZT sublayers were observed in the samples B and D. The effect of the crystalline quality of the STO substrate on the quality of the YBCO and PZT epitaxial films was discussed.

The modulation structure in the be plane of a phase-separated Cu-rich La2CuO4.003 oxide was studied using transmission electron microscopy. Upon an electron beam irradiation at 93 K, a phase transformation from superconducting phase to antiferromagnetic phase was observed and identified based on the analysis of the different reflection conditions for the two space groups of the two phases, i.e., D-2h(23) or Fmmm for the superconducting phase and D-2h(18) or Bmab for the antiferromagnetic phase. For the superconducting phase it is found that the modulation vector changes from 0.041[06 (8) over bar]* toward 0.027[04 (8) over bar]* during the electron-beam irradiation. Electron energy-loss spectroscopy results are also presented showing that the Cu-rich La2CuO4.003 oxide has indeed phase-separated into hole-rich superconducting phase and hole-poor antiferromagnetic insulating phase. [S0163-1829(99)00505-6].

We investigate the photoinduced quasiparticle dynamics in the electron-doped superconductor La2-xCexCuO4 (LCCO) by using femtosecond pump-probe technique. A monoexponential decay function is employed to fit the data for the first 20 ps after the maximum of the signal. The relaxation time decreases with increased temperature both above and below T-c. Power function (tau proportional to T-N) is used to fit the relaxation time. N is 1.45 for above 20 K and 0.3 for below 20 K. The change of N at 20 K is. attributed to the opening of the gap. (c) 2005 Elsevier B.V. All rights reserved.

Pt/(Ba0.7Sr0.3)TiO3 (BST)/YBa2Cu3O7−x capacitors were prepared and investigated for the dead-layer (DL) thickness (td) and the DL dielectric constant (ed). Based on the series capacitor model, the td/ed ratio of 0.066 nm and the bulk BST ferroelectric-layer dielectric constant of 1370 were obtained through the measurements of the capacitance–voltage characteristics. The td×ed value of 120 nm was obtained through the measurements of the current–voltage characteristics. Combining these data, the DL thickness and the DL dielectric constant are respectively estimated to be 2.8 nm and 42.6.

We have systematically studied the resistive transition of multilayers of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$/${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ (YBCO/PBCO) under different perpendicular magnetic fields. It was found that the resistive transition is dominated by the flux-thermal-activation process; the broadening of the resistive transition was observed with the same order as that in single-layer thin films and the resistivity obeys the relation \ensuremath{\rho}=${\mathrm{\ensuremath{\rho}}}_{0}$ exp(-U/kT). The activation energy depends logarithmically on the applied magnetic fields and decreased linearly with temperature. This phenomenon may be attributed to the creation of edge-dislocation pairs in the two-dimensional pancake vortices situated in the individual YBCO layer. The possible pinning mechanisms in the multilayers are discussed.

A low cost reproducible fabrication process has been developed to prepare La0.5Ca0.5MnO3 (LCMO) films with well distributed uniform nanoscale dots using pulsed-laser deposition. It was found that the growth of the dots was closely related to the strain in the film during the growth process. The diameter and density of dots could be controlled within the range of 30–120 nm and 2×108–2×109/cm2, respectively. The magnetoresistance effect of such LCMO films is also enhanced, which may be caused by the spin-dependent scattering of carriers due to the existence of the dots.

Some electromagnetic properties of the η-pairing eigenstate of the Hubbard model are investigated. The persistent current density Js in the eigenstate is discussed, and the distribution of magnetic field in the studied periodic lattice is analyzed. It is shown that the behaviour of the electromagnetic response is peculiar. Einige elektromagnetische Eigenschaften des η-Paarungs-Eigenzustandes des Hubbard-Modells werden untersucht. Die konstante Stromdichte Js im Eigenzustand wird diskutiert und die Verteilung des Magnetfeldes in der untersuchten, periodischen Struktur wird analysiert. Das Verhalten des elektromagnetischen Responses weist Besonderheiten auf.

Flux pinning and anomalous magnetization peak of heavily overdoped Bi2−xPbxSr2CaCu2−yCryO8+δ [Cr-doping (Bi, Pb)-2212] single crystals are investigated by means of magnetization measurements with the magnetic field parallel to the c axis. Compared with undoped Bi2Sr2CaCu2O8+δ (Bi-2212) and Pb-doping Bi2−xPbxSr2CaCu2O8+δ [(Bi, Pb)-2212] single crystals, the irreversibility line of Cr-doping (Bi, Pb)-2212 single crystals is pronouncedly shifted to high temperatures. The anomalous magnetization peak H2p with maximum peak field near 8000 G is observed. The H2p exhibits strong temperature dependence from 0.19 to 0.93Tc. The temperature dependence of H2p can be explained according to vortex decoupling theory. The improved flux pinning may originate from reduced anisotropy due to Pb doping and a sufficient number of effective pinning centers due to the random Cr substitution on the Cu site.

Using Zn thin film as counterelectrode, Bi2Sr2CaCu2O8+δ tunnel junctions were prepared. Temperature-dependent tunneling spectra of these planar junctions provided measurements of energy gap, 2Δ, and transition temperature, Tc. The spectra also allowed the observation of pseudogap in normal state and showed strong evidence of d-wave symmetry of the superconducting order parameter. The present junction may find its way in the electronics applications.

In this letter we present an investigation on probing leakage current and ferroelectricity of Pb(Zr, Ti)O3(PZT)/YBa2Cu3Ox heterostructure using a modified atomic force microscopy. Inhomogeneities of leakage current and ferroelectric properties were concurrently mapped and quantitatively studied on a nanometer scale. It shows that microscopically the leakage current can be described by a model based on space-charge-limited current.

We demonstrate the operation of a deterministic fluxon ratchet made of a stack of 30 intrinsic ${\text{Bi}}_{2}{\text{Sr}}_{2}{\text{CaCu}}_{2}{\text{O}}_{8}$ Josephson junctions. The ratchet has the shape of a gear with 20 asymmetric teeth (periods). It produces a rectified voltage of about $100\text{ }\ensuremath{\mu}\text{V}$ at a 12 GHz drive frequency. The effect of coupling between intrinsic junctions, i.e., the mode of fluxon motion for ratchet operation, has been studied within the framework of the two-dimensional coupled sine-Gordon equations. Further, we used low-temperature scanning laser microscopy to demonstrate that voltage rectification indeed is due to directed fluxon motion, in agreement with numerical simulations.

A series of c-axis oriented electron-doped high-Tc superconducting La(2-x)CexCuO4 thin films, from heavily underdoped x=0.06 to heavily overdoped x=0.19, have been synthesized by dc magnetron sputtering technique on (100) SrTiO3 substrates. The influence of various fabrication conditions, such as the deposition temperature and the deposition rate, etc., on the quality of the thin films has been scrutinized. We find that the quality of the films is less sensitive to the deposition temperature in the overdoped region than that in the underdoped region. In the phase diagram of Tc(x), the superconducting dome indicates that the optimally doping level is at the point x=0.105 with the transition temperature Tc0 = 26.5 K. Further more, both the disappearance of the upturn in the $\rho_{xx}$(T) curve at low temperature under H=10 T and the positive differential Hall coefficient, $R_H'=d \rho_{xy}/dH$, are observed around x = 0.15, implying a possible rearrangement of Fermi surface at this doping level., Comment: 5 pages, 5 figures

We investigate the low-temperature Hall effect in electron-doped ${\text{La}}_{2\ensuremath{-}x}{\text{Ce}}_{x}{\text{CuO}}_{4}$ thin films from heavily underdoped $x=0.06$ to heavily overdoped $x=0.17$. With increasing $x$, the charge carriers that dominate the Hall effect gradually change from electronlike to holelike. From the Hall coefficient and differential Hall coefficient, we infer that a large holelike Fermi surface forms above $x=0.15$, that is, the electronlike pocket may exist until $x=0.15$. Meanwhile, the sign of the Hall resistivity changes from negative $(x=0.105)$ to positive $(x=0.12)$ at 2 K, indicating that single electron pocket exists below $x=0.105$ at low temperature.

The a‐ and c‐axis‐oriented YBa2Cu3O7−y thin films were prepared by rf magnetron sputtering technique. The characterization of the thin films was carried out by inductively coupled plasma atomic emission spectroscopy, x‐ray diffraction, and scanning Auger profile techniques. The Tc, Tc(H), Jc(H), and Hc2 ‐T(near Tc) were measured by the standard dc four‐probe method. It was found that very strong anisotropy of this material was manifested in its superconducting properties, especially for c‐axis‐oriented thin films. It was also found that Jc depends very strongly upon stoichiometric composition 123, preferential orientation of the film, and the characteristic of the film‐substrate interface.

Formation of an ordered surface structure in La0.5Ca0.5MnO3 films due to the mismatch of the thermal expansion coefficient between the film and the substrate has been investigated. The surface pattern consists of grain chains located on regular orthogonal cracks. The cracks serve as weak-link grain boundaries, and unusually enhanced low-field magnetoresistance (−14.4% in 400 Oe at 90 K) has been observed, which may be explained by spin-polarized tunneling across the grain boundaries.

Sr0.35CoO2 and Ca0.38CoO2 single crystals have been successfully prepared by a low-temperature ion exchange of layered NaxCoO2 precursors. Both samples are isostructural to NaxCoO2 with the layered triangular structure. Low-temperature susceptibility, specific heat, and resistivity are measured. For both samples, the magnetic susceptibility shows a Curie-Weiss behavior at high temperatures and exhibits a broad peak at low temperatures, characteristic of two-dimensional antiferromagnetic fluctuations. For Sr0.35CoO2 crystal, the resistivity is metallic in the whole temperature range and the specific heat below 10 K can be well described by a sum of the electronic and lattice contributions. In the case of Ca0.38CoO2 crystal, the resistivity exhibits a metallic behavior above 25 K, while a transition from metal to insulator for rho(c) below 25 K is observed. The low-temperature specific heat for Ca0.38CoO2 crystal can be well fitted by a sum of the electronic, lattice, and exponential contributions. A gap feature in electronic excitation spectra is observed, and this opening of the gap may account for the metal to insulator transition in resistivity measurement.

Highly (100) oriented Pb(Zr0.53Ti0.47)O3 (PZT) films were prepared on Si substrates with ultrathin SiO2 buffer layer by pulsed laser deposition. Hysteresis measurements show that saturation polarization, remnant polarization and coercive field of the films reach 26 μC/cm2, 10 μC/cm2 and 70 kV/cm, respectively. The thickness of SiO2 buffer layer is found to play a significant role on phase purity and orientation of PZT as well as the prevention of interdiffusion. It is also found that the grain size and the interdiffusion between PZT and Si are the key factors for the ferroelectric properties of the films, which are discussed together with the synthesis condition in detail.

We use interfacial transport and transmission electron microscopy to study the $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}(\mathrm{YBCO})∕{\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}\mathrm{Mn}{\mathrm{O}}_{3}(\mathrm{LCMO})$ junction that form a ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$-wave superconductor and a ferromagnet (FM) heterostructure. Zero bias conductance peaks (ZBCPs) caused by Andreev reflection at zero bias were observed in the interfacial differential conductance spectra for the sample with an orderly mixed $c$- and $a$-axis [with (001) and $(100)∕(110)$] orientation of YBCO in the interface. When the YBCO film is oriented with the $c$-axis normal to the interface, a zero bias conductance dip (ZBCD) is observed. These results evidence the existence of surface Andreev bound states (midgap states) in the {110} surface of YBCO, which can lead ZBCP to appear in all directions except the {100} surface of YBCO where ZBCD occurs. Furthermore, the absence of any obvious influence of spin-polarization of LCMO on ZBCP in zero magnetic field implies that the LCMO is not half-metallic in the interface of $\mathrm{YBCO}∕\mathrm{LCMO}$, while strong magnetic field dependence of ZBCP shows that the applied magnetic field enhances the spin polarization of LCMO and suppresses ZBCPs in YBCO.

Two-dimensional (2D) vortex dynamics is studied in ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}/{\mathrm{PrBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ superlattices by measuring the current-voltage $(I\ensuremath{-}V)$ characteristics. In the high current limit, the 2D collective creep is observed with an activation energy $U(j)\ensuremath{\propto}{j}^{\ensuremath{-}\ensuremath{\mu}},$ with j the current density. The exponent $\ensuremath{\mu}$ is 0.8 at low temperatures and $\ensuremath{\mu}=0.2$ at high temperatures. A dislocation-mediated vortex melting occurs when the temperature is increased. In the low current limit, the exponential growth of the energy barrier for elastic motion is prohibited by the plastic deformation of vortices. The observed plateau in the resistive transition is attributed to the possible quantum tunneling of vortices.

We investigate vortex pinning in thin superconducting films with a square array of rectangular submicron holes ("antidots"). Two types of antidots are considered: antidots fully perforating the superconducting film and "blind antidots," holes that perforate the film only up to a certain depth. In both systems, we observe a distinct anisotropy in the pinning properties, reflected in the critical current I-c, depending on the direction of the applied electrical current: parallel to the long side of the antidots or perpendicular to it. Although the mechanism responsible for the effect is very different in the two systems, they both show a higher critical current and a sharper I-V transition when the current is applied along the long side of the rectangular antidots.

Molecular-dynamics simulations of the current-voltage characteristics V(I) have been performed for regular arrays of asymmetric pinning centers modeled by the superposition of two interpenetrating square lattices of weak and strong pinning centers with separation Deltap. In this case, an applied Lorentz force F-L acts as a depinning force which is directed either from weak to strong pinning site or vice versa, depending on the polarity of F-L. This leads to a pronounced asymmetry of the current-voltage characteristics and of the critical currents I-c(F-L) and I-c(-F-L) ("vortex diode effect"). In addition to that, the F-L-Deltap phase diagram reveals a strong dependence of the different dynamical vortex phases on the shift between the two pinning sublattices.

The Hall effect study has been performed to examine the nature of quasi-particles of electron-doped superconductor, T′-phase La2−xCexCuO4 (LCCO) thin films with 0.06 ⩽ x ⩽ 0.17 , for which the superconductivity is quenched by magnetic fields (up to 12 T) at temperature well below T c . The data distinctly show the evolution of the role of electron-like and hole-like quasi-particles in Fermi surface which dominate the superconductivity and normal state transport.

The new superconducting system Sr2VO3-delta FeAs has been fabricated at different oxygen contents. It is found that the superconducting transition temperature drops monotonically with the increase of oxygen deficiency and the residual resistivity, indicating an anomalous pair breaking effect by disorders. Magnetotransport measurements reveal that the superconducting transition evolves from one-step-like at low field to two-step-like at high field. The first step corresponds to the upper critical field, while the second one is related to the irreversibility line. A vortex phase diagram is thus derived, which shows a large area of vortex liquid state. This indicates a high anisotropy of the system. Finally we present the specific heat of the optimally doped sample (delta approximate to 0.1) with T-c = 40 K. A high residual specific heat coefficient appears in the superconducting state, suggesting the existence of large amount of unpaired electrons which may derive from the V-band. (C) 2010 Elsevier B.V. All rights reserved.

We have successfully fabricated epitaxially grown YBa2Cu3O7/PrBa2Cu3O7 (YBCO/PBCO) multilayer thin films on SrTiO3 and LaAlO3 substrates by dc/rf magnetron sputtering. The thicknesses of YBCO and PBCO varied from 1 to 8 unit cells. Satellite peaks in x‐ray diffraction patterns clearly indicate the formation of periodic modulation structures of different wavelengths. At a certain thickness of the YBCO layer, the zero resistance transition temperature Tc0 decreased with the increase of the PBCO layer thickness. In contrast, Tc0 increased with the increase of the YBCO layer thickness at a constant PBCO layer thickness.

An incommensurate modulation has been observed in a Cu-rich La2CuO4.003 crystal. It is shown that the modulation results from a periodically distributed holes lying on the CuO2 planes, and that the hole modulation may be regarded to be a kind of valence modulation. It is shown that appreciable valence modulation contrast may be generated by the mechanisms of hole scattering alone when the period of the modulation is of the order of 2 nm.

We investigate the in-plane transport and magnetic properties of La1.89Ce0.11(Cu1-xCox)O-4 thin films with x = 0.01-0.05. With increasing Co concentration, T-c is obviously suppressed and a crossover from superconductor to insulator at low temperature is observed, and the negative Hall coefficient is enhanced. All the Co-doped samples exhibit long-range ferromagnetic ordering even at the room temperature by magnetic measurements. (C) 2007 Elsevier B.V. All rights reserved.

The oxide spinel Li1+xTi2-xO4 exhibits superconductivity with many similarities with copper oxide superconductors. Li1+xTi2-xO4 powder was synthesized by the solid-state reaction method. The samples show a superconducting transition temperature up to 13.7 K when x = 0. The superconductivity persists till x = 0.1. In the normal state, the resistivity shows a metal-insulator transition by increasing x. The similarity between the Li1+xTi2-xO4 and high T-c cuprates has been compared and a qualitative analysis of the metal-insulator transition has been given. (c) 2007 Elsevier B.V. All rights reserved.

Detailed resistivity measurements were made for polycrystalline Hg1-xTlxBa2Ca2Cu3O8+delta (x = 0.2) in zero field and in the temperature region from zero resistance up to 300 K. The fluctuation conductivity Deltasigma was analyzed as a function of is an element of equivalent to In(T/Tc-mf) in the range -5.5 < Inc < -0.5. 1D behavior Of fluctuation conductivity was found at high temperatures (above the 2D regime) with a crossover temperature T-1*, above which the critical exponent was found to be -1.5. (C) 2004 Elsevier B.V. All rights reserved.

Detailed resistivity measurements were made for polycrystalline Hg1-xTlxBa2Ca2Cu3O8+delta (x = 0 and 0.2) in zero field and above the superconducting T-c. The fluctuation conductivity Deltasigma is analyzed. With decreasing temperature two crossover temperatures could be identified for each sample; i.e. T* from two to three dimensional fluctuations in the mean field region (MFR), and T-G from the MFR to the critical region. All results are in agreement with the Lawrence-Doniach model. The c-axis coherence length and the interlayer coupling factor were obtained. (C) 2003 Elsevier Science B.V. All rights reserved.