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We present the results of superconductivity, normal state magnetic susceptibility and heat capacity measurements on the tetragonal CaLa 1-x Pr x BaCu 3 O 7 compound. Ac susceptibility measurements show that the transition temperature T c of the unsubstituted sample decreases with an increase in the Pr concentration. Normal state dc magnetic susceptibility measurements performed in an applied field of 0.5 T show a Curie–Weiss behaviour in terms of the paramagnetic moment of Pr. The effective paramagnetic moment of Pr appears to be intermediate between those of the free Pr 3+ and Pr 4+ ions. For the nonsuperconducting samples i.e., x = 0.70 and 1.0, we observe an antiferromagnetic ordering temperature T N of nearly 4 K and 8 K respectively. The X-ray diffraction results show that the CaPrBaCu 3 O 7 compound is free from other phases, having a minor (less than 8%, in terms of peak intensity) impurity phase. The lower T N (8 K) of PrBaCaCu 3 O 7 as compared to the known antiferromagnetic ordering temperature of 17 K for PrBa 2 Cu 3 O 7 indicates a less deleterious effect of Pr in the present case.

Resistivity and ac susceptibility of Zn-doped samples of the LaBaCaCu{sub 3}O{sub 7{minus}{delta}} (LBCCO) system have been measured for Zn content of 0.5{percent}, 1.0{percent}, 1.5{percent}, 2.0{percent}, 2.5{percent}, and 3.0{percent} at.wt. X-ray diffraction has been used to find the lattice parameters of the samples. The samples remain tetragonal for all the considered concentrations of Zn. Idometry and thermogravimetric analyses have been done to estimate the oxygen content of different samples. Analyzing the resistivity and ac susceptibility data, the following conclusions are drawn about the role of Zn in the LBCCO samples. (1) The conduction mechanism of electrons appears to follow a crossover from the purely metallic regime to the localization regime due to either weak localization or electron-electron interaction effects after about 1.5{percent} Zn. (2) The superconducting transition as revealed by the resistivity vs temperature curves or susceptibility vs temperature curves becomes sharper with Zn increasing content of Zn up to 1.0{percent}. After 1.5{percent} the resistive and ac susceptibility transitions become broader with increasing Zn. (3) T{sub c} depression up to Zn content of 1.0{percent} seems due to direct suppression of the effective pairing interaction, while at and above 2.5{percent} Zn T{sub c} depression is expected to be due to disorder effectsmore » such as reduction of density of states at the Fermi energy. {copyright} {ital 1997} {ital The American Physical Society}« less

ZrB${}_{2}$ is a nonsuperconducting Pauli paramagnetic crystallizing in the AlB${}_{2}$ structure. V substitution for Zr in Zr${}_{1\ensuremath{-}x}$V${}_{x}$B${}_{2}$ (0.01 $\ensuremath{\le}$ $x$ $\ensuremath{\le}$ 0.1) at the few percentage level induces superconductivity with critical temperature reaching a maximum of 8.7 K for Zr${}_{0.96}$V${}_{0.04}$B${}_{2}$ near the solid solubility limit. Specific-heat and lower critical field temperature dependence results suggest the possibility of unconventional superconductivity possibly arising from multiband effects.

The effect of CuO substitution by MS ( M = Ni, Fe or Zn) in (Y-123) samples is studied by DC resistivity, AC susceptibility and x-ray emission spectroscopy and diffractometry. All samples show sharp x-ray diffraction patterns with no impurity phase lines for M = Ni, Fe or Zn-doped samples. The cell of Ni-, Zn- or Fe-substituted Y-123 samples remains orthorhombic for all concentrations studied. X-ray emission spectroscopy results show that sulphur atoms enter the lattice of Y-123 compounds and form oxyanion groups. The diamagnetic transitions are sharp for all the small concentrations and become broad for MS doping above 10%. The transition temperature decreases with increasing MS concentration when compared with the undoped sample.

Both on-site Zn substitution and oxygen deficiencies in the CaLaBaCu 3 O 7 system decrease the superconducting transition temperature T c of the pristine sample. We observed that the normal state magnetism, measured in a field of 5 KOe, shows a Curie-Weiss behavior, in terms of a localized magnetic moment, presumably on Cu sites, in both cases. The pristine system, i.e. without Zn substitution or oxygen deficiencies, shows a weakly temperature dependent small magnetic susceptibility, in the normal state, i.e. above T c . It has been argued that the normal state magnetism of HTSC systems plays a vital role in determining the T c of these materials.

A chitosan-based ferrimagnetic membrane (Chitosan/NiFe2O4) was prepared and it showed a typical magnetization of soft ferrimagnetic material with Ms=16 emu/g at 50 kOe and a high capacity to extract Hg(II), Cu(II) and Zn(II) ions from aqueous solutions. These results indicate that the Chitosan/NiFe2O4 is a good candidate to remove heavy metals from polluted water with the possibility that its recovery can be done by an electromagnet.

A complex perovskite oxide YSr2SbO6 has been synthesized by solid-state reaction. Structural ordering in this material has been studied by X-ray diffraction. The X-ray diffraction pattern reveals that YSr2SbO6 has an ordered complex cubic structure characteristic of A2BB′O6 crystalline structure with lattice constant a=8.2561 A. The chemical stability of YSr2SbO6 with YBa2Cu3O7−δ superconductors has been studied by X-ray diffraction and magnetic measurements on YSr2SbO6/YBa2Cu3O7−δ composites. Magnetic measurements show that superconducting transition temperature of pure YBa2Cu3O7−δ and YSr2SbO6/YBa2Cu3O7−δ composites is 90 K. These studies show that YSr2SbO6 could be a potential candidate as a substrate material for films of YBa2Cu3O7−δ. Furthermore, Percolation threshold VC and critical exponent t are found in the YSr2SbO6, YBa2Cu3O7−δ composite.

Using the Ginzburg-Landau (GL) theory, we calculate the stability of sample symmetry-induced vortex-antivortex molecules in a mesoscopic superconducting bilayer exposed to a homogeneous magnetic field. We demonstrate the conditions under which the two condensates cooperatively broaden the field-temperature stability range of the composite (joint) vortex-antivortex state. In cases when such broadening is not achieved, a reentrance of the vortex-antivortex state is found at lower temperatures. In a large portion of the phase diagram noncomposite states are possible, in which the antivortex is present in only one of the layers. In this case, we demonstrate that the vortex-antivortex molecule in one of the layers can be pinned and enlarged by interaction with a vortex molecule in the other. Using analogies in the respective GL formalisms, we map our findings for the bilayer onto mesoscopic two-band superconductors.

The influence of superficial defects on the vortex configurations of a thin superconducting disk is investigated within the time dependent Ginzburg-Landau formalism. The free energy, magnetization, vorticity, and the Cooper pair density are calculated for both metastable and stable vortex configurations and different number of defects on its surface in the presence of an external magnetic field applied perpendicular to the disk area. We show that the competition between the confinement geometry and the geometric position of the defects leads to non-conventional vortex configurations which are not compatible with the symmetry of the sample geometry. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.

In this paper we report on the synthesis and the structural, electrical, magnetic and thermal analysis for the new material (0.01 x 0.05). A superconducting transition was observed for all x values studied, despite the non-superconducting matrix ZrB2, which indicates that the superconducting state is induced by the presence of Nb. The results show that the critical temperature increases with Nb content, reaching its maximum (T c = 8.1 K) for x = 0.04. From the specific heat data we find a Sommerfeld constant of γ = 1.6 mJ molK−2 and a Debye temperature of = 615.5 K. Unconventional behaviors are observed in specific heat dependence with temperature and in diagram. These behaviors are investigated in versus T curve, where an upturn appears for K, and in versus dependence, which shows a clear deviation from BCS theory for low temperatures. Also, contrary to the conventional theories we found a positive curvature for temperatures near T c in the lower critical field, besides an upturn around 2.3 K. We suggest that these behaviors possibly arise from multiband superconductivity in .

Estudiamos la temperatura óptima para favorecer el crecimiento epitaxial de capas de YBa2Cu307 (YBCO) utilizando tres temperaturas de sinterizado de 820, 840 y 860℃, mediante el método dedeposición de solución química sobre sustratos monocristalinos, SrTiO3 [100]. La morfología superficialfue obtenida a través de imágenes ópticas, caracterizando cualitativamente la homogeneidad y lapresencia de granos a lo largo del eje c. La difracción de rayos X confirma el crecimiento epitaxialpreferencial (00l) de los cristalitos del YBa2Cu307, obteniéndose una mayor intensidad de los perfiles(00l) para la temperatura de 860℃. Las muestras resultaron superconductoras con temperatura críticade 90 K, para los tres casos., We studied the optimun temperature to favor the epitaxial growth of YBa2Cu3O7 layers using threesintering temperatures of 820, 840 and 860℃, by the chemical solution deposition method in SrTiO3[100] monocrystalline substrates. Surface morphology was obtained by optical imaging, which qualitativelycharacterize the homogeneity and the grain presence along the c-axis. The X-ray diffractionconfirms the preferential epitaxial growth (00l) of the YBa2Cu3O7 crystals, resulting in a higher intensityof the profiles (00l) for the temperature of 860℃. The samples shown superconducting behaviourat critical temperature of 90 K, for the three cases.

We investigate experimentally and theoretically the vortex dynamics in a superconducting film with nanoengineered open vortex traps which provide tunable pinning, ranging from no pinning for a certain current direction to finite pinning when reversing the current flow. The design is based on the confinement of the vortex motion within two repulsive walls, one with periodic microprotrusions and the other one smooth. Clear commensurability effects are seen if the bias current drives the vortices inside the traps, whereas these effects are much less pronounced when the current pushes the vortices against the smooth surface. For small periods of the protrusions or large vortex sizes, the properties displayed by the vortices, pushed against these two surfaces of dissimilar roughness can be thought of as due to the change of effective sliding friction. © 2011 American Physical Society.

We report measurements of magnetization and diamagnetic susceptibility in polycrystalline LaBaCaCu3O 7− δ in high magnetic fields (20–50 kOe). The sample has a zero-field transition temperature T c0 =77 K and a transition width of 2.0 K. The results show large fluctuation effects, which can be explained by Ginzburg–Landau fluctuation theory for a two-dimensional system. Using a theoretical model based on the lowest Landau-levels approximation, the magnetization data are fitted with good agreement. The weak-field fluctuation diamagnetic susceptibility above T c can be fitted well in terms of the 2D Lawrence–Doniach model.

We present X-ray and magnetization results for the compound [Y0.75Ca0.25]SrBaCu3−x(PO4)xOy with 0.0⩽x⩽0.30 synthesized at normal pressure and temperature. X-ray diffraction patterns show that for x= 0.0 the compound crystallizes into an orthorhombic phase. For increasing x a tetragonal phase is obtained. The Rietveld method was used to refine lattice constants. The magnetization measurements show that the samples were all superconductors over a range of temperatures from 10 to 100 K. The diamagnetic transition temperature Tc decreases with increasing (PO4)3− concentration (Tc=55 K for x=0.0 and Tc=35 K for x=0.30).

AC susceptibility measurements and normal state magnetism have been carried out on LaBaCaCu 3− x M x O 7− δ (RE : 1113) system, where M=Co, Ni, Ga with 0 x T c ) of the pristine sample, determined from the measurements of both real and imaginary parts of AC susceptibility, decreases with increasing dopant concentration ( x ) of all the three cations. T c depression rate with doping concentration (d T c /d x ) follows the order Ga>Co>Ni. The normal state DC magnetism implies a localized moment presumably on doped M ions for Co and Ni and an induced magnetic moment for Ga-doped system, of nearly 0.5 μ B , supposedly residing on Cu ion.

We investigated theoretically vortex configurations in thin mesoscopic superconducting equilateral triangles submitted to an external magnetic field. Analytical expressions for the vortex interactions with the screening current and other vortices were calculated by considering the sample sides much smaller than the effective penetration depth within the London limit. The vortex configurations were obtained by using Langevin dynamics simulations. In most of the configurations, the vortices sit close to the corners, presenting twofold or threefold symmetry. We also determined the dependence on the magnetic field of the equilibrium states. The ground states with larger magnetic field range are those with the number of vortices equal to the triangular numbers [${N}^{\ensuremath{'}}=n(n+1)/2$, with $n$ integer]. A study of different stable configurations with the same number of vortices is also presented.

Petrucio Barrozo,1,2 Andre A. Moreira,1 J. Albino Aguiar,2 and Jose S. Andrade, Jr.1,3 1Departamento de Fisica, Universidade Federal do Ceara, 60455-760 Fortaleza, CE, Brazil 2Departamento de Fisica, Universidade Federal de Pernambuco, 50670-901 Recife, PE, Brazil 3National Institute of Science and Technology for Complex Systems, Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ, Brazil Received 28 August 2009; published 28 September 2009

Geometrical and electrical properties of crumpled wires are investigated. Power laws connecting the geometrical and electrical properties of these random systems are studied and critical exponents are calculated. In particular the authors have obtained the resistance exponent zeta which seems to be compatible with a previous conjecture.

We have performed an experimental study of magnetic and magneto‐transport properties on a polycrystalline sample of RuSr2GdCu2O8. (Ru‐1212). Two peaks in the derivative of the resistive curves were identified in the temperature T1 = 43 K and T2 = 34 K at zero magnetic field. The magnetization presents an increase, at the same temperature T2 of the resistive curves, followed by a decrease at lower temperatures, which leads to the appearance of a peak in the magnetization versus temperature plots upon entering of superconducting state. We discuss how the anomalies observed in the magnetic and electric measurements could be originated by fault in the stoichiometric of Ru‐1212.

This work presents a simple model for the thermal growth of SiO2 thin films on silicon substrates which may shed some light on the theory of silicon oxidation processes. In the model it is assumed that the time rate evolution of the oxidized region is proportional to the average number of non-oxidized silicon sites in a transition region. As a consequence, the oxide thickness x is found to scale with the oxidation time as x approximately tb in agreement with a large number of experimental data. The value of the exponent b is found to be in the range of 1/2

The vortex-dominated ac response of a superconducting film with a periodic array of pinning centers is studied in the linear regime for vortex densities greater than the saturation number. A simple model is introduced to describe small oscillations of the vortex lattice, which is considered to be composed of two distinct lattices formed by trapped vortices and interstitial vortices. The frequency-dependent complex resistivity is calculated as a function of frequency and magnetic induction for vortex densities between the first and the second matching fields. It is shown that the absorption spectra has two peaks corresponding to two characteristic pinning frequencies: one due to the periodic pinning array and another due to vortex-cage pinning. The range of validity of the model is determined from direct numerical simulations.

Fabrication of superconducting layered systems offers fascinating possibilities to observe novel superconducting phenomena. In this work we study a new nanostructured superconducting trilayer. Nb/Pb/Nb trilayer was grown by magnetron sputtering and the superconducting properties were studied via magnetic and electrical transport measurements. The magnetization and resistivity have been analyzed as functions of the temperature and magnetic field applied perpendicularly to the layers. The sample presents sharp resistive and magnetic transitions at TC = 7.2 K. Vortex avalanches attributed to thermomagnetic instabilities were observed in magnetization versus applied field loops. The temperature dependence of μ0Hc2 presents a positive upward curvature at low temperatures, indicating a crossover which is consistent with the Takahashi–Tachiki model for superconducting superlattices. The temperature dependence of the lower critical field μ0Hc1(T) presents an unconventional feature consistent with a multicomponent behavior with spatially separated components.

We study the optimal temperature to obtain YBa2Cu3O7-δ epitaxial films grown onto SrTiO3 substrates by direct solution deposition. The samples received heat treatment at 820, 840 and 860 °C, then characterized by XRD, observing the (00l) profiles; and magnetic susceptibility measurements. The TC-onset for all the samples was 90 K. In addition, the current – voltage (I-V) measurements shows typical tunneling signals corresponding to normal metal-superconducting junctions indicating the films are promising for potential electrical applications.

Vortices in a narrow superconducting strip with a square array of pinning sites are studied. The interactions of vortices with other vortices and with external sources (applied magnetic field and transport current) are calculated via a screened Coulomb model. The edge barrier is taken into account and shown to have an important role on the system dynamics. Numerical simulations in this approach show that the field dependent magnetic moment presents peaks corresponding to history dependent configurations of the vortex lattice. Some effects of the edge barrier on the I-V characteristics are also reported., Comment: 4 pages, 3 figures

Se sinterizaron muestras de [Y1-xCax]SrBaCu2.80(PO4)0.20Oy con 0,10≤x≤0,40 usando la técnica de reacción de estado sólido. Los patrones de difracción de rayos-x muestran que todos los compuestos cristalizaron en una estructura tetragonal 123. El análisis de la estructura con refinamiento de Rietveld, se hizo usando un modelo que contiene un Cu(2) en coordinación cuatro y no en cinco como en las otras estructuras tetragonales 123. Este hecho permite que Tc aumente con la concentración de Ca. Tal como se reportó en un artículo anterior, todas las muestras son superconductoras., [Y1-xCax]SrBaCu2.80(PO4)0.20Oy samples with 0.10 ≤ x ≤ 0.40 were syntherized using the solid state reaction technique. X-ray diffraction patterns show that all the compounds crystallized into a 123 tetragonal structure. The analysis of the structure with Rietveld refinement were made using a model that contains one Cu(2) in four coordination and not in five coordination as in the other 123 tetragonal structures. This fact allows that Tc increase with Ca concentration. All samples are superconductors as reported in a previous paper.

Se sinterizaron compuesto de [Y0.75Ca0.25]SrBaCu3-x(PO4)xOy dopados con (PO4)3-, para 0,0≤x≤0,30 usando la técnica de reacción de estado sólido en condiciones de presión y temperatura normales. El patrón de difracción de rayos-X muestra que para x=0,0 la meustras cristalizan en una fase ortorómbica y para otros valores de x las muestras presentan una estructura tetragonal. Se utilizó el método Rietveld para refinal las constantes reticulares. El análisis de estructura con refinamiento de Rietveld se hizo usando un modelo que contiene un Cu(2) en coordinación -4 y no en coordinación -5 como en las otras estructuras tetragonales 123. Todas las muestras son superconductoras como se reporta anteriormente [1]., (PO4)3- doped [Y0.75Ca0.25]SrBaCu3-x(PO4)xOy compounds with 0.00 ≤ x ≤ 0.30 were synthesized using the solid state reaction technique at normal pressure and temperture conditions. The X-ray diffraction patterns show that for x= 0.0 the samples crystallize into an orthorhombic phase, and for other x values the samples presented a tetragonal structure. The Rietveld method was used to refine the lattice constants. The analysis of structure with Rietveld refinement was done using a model that contains one Cu(2) in a four coordination and not in five coordination in the other 123 tetragonal structures. All samples are superconductors as reported previously [1].

The time dependent Ginzburg–Landau equations (TDGLE) are used to study the properties of a mesoscopic superconducting square surrounded by different metallic materials. The properties of the metallic environment are taken into account by De Gennes boundary conditions, via the extrapolation length b . The external magnetic field is applied perpendicularly to the square surface. The TDGLE are used upon taking the magnetic field and the order parameter invariant along z -direction. It is determined the b -limit for the occurrence of a single vortex in a mesoscopic square of area d 2 , d varies discretely from 4 ξ (0) to 10 ξ (0). We can show a logarithmical dependence of the sample size as a function on b parameter.

Vortex configurations are studied in thin superconducting type II disks with finite Λ = 2 λ 2 / d (where d and λ are the disk thickness and the London penetration depth), with an external magnetic field applied parallel to the disk symmetry axis. The screening currents were obtained numerically within the London approach. The Pearl vortex interaction was approximated by ∼1/ r ( r + Λ ), which allows to treat the boundary condition by adding a vortex image outside the disk. Stable vortex configurations were obtained by numerically integrating the Bardeen–Stephen equation of motion. For decreasing magnetic field different sequences of vortex states develop, which depend on the R / Λ ( R is the disk radius). Moreover, the distribution of vortices does not seem to show a strong dependence on R .

We solve numerically the nonlinear TDGL equations to study the vortex dynamics in a mesoscopic type II cylinder superconductor containing one rectangular hole in the presence of an external field applied perpendicular to the surfaces. We calculate the spatial distribution of the superconducting electron density and the phase of the superconducting order parameter using the numerical method based on the technique of gauge invariant variables. It is assumed that the inner hole edge is in contact with a material whose properties are accounted in the de Gennes boundary conditions with a parameter b (de Gennes extrapolation length), while the outer edge is in contact with vacuum. The dynamics of different vortex states and the magnetization curves are studied as a function of the external magnetic field.

CaLaBa superconductor is a protorype of the YBa structure

We have investigated the critical current density (Jc) and the flux pinning behavior in Zr0.96V0.04B2 superconductor with an AlB2 structure. V substitutions in Zr sites of non-superconducting ZrB2 system lead to superconductivity, and the 4% V-substituted Zr0.96V0.04B2 compounds show the highest superconducting transition temperature (Tc) of ∼8.7 K. The magnetic hysteresis (M−H) loops for the Zr0.96V0.04B2 demonstrate type-II superconducting behavior in a broad temperature range, and the Jc is estimated from the M−H loops using the Bean model. The analysis of the double-logarithmic Jc(H) plots indicates the dominance of collective pinning in Zr0.96V0.04B2, and that Jc(H) and magnetic field dependences of the flux pinning force density (Fp) are well fitted by the double exponential model which takes into account the existence of two superconducting gaps.

In this paper, we report on the influence of a square (triangular) trench on the superconducting properties of a perforated mesoscopic sample. Effects associated to the pinning force of the hole versus the pinning by the trench and interplay between the shape of the outer boundary and the shape of the inner defects on the vortex configuration are studied for a thin disk. Using the Ginzburg–Landau theory, we calculate the magnetization, vorticity, free energy, magnetic induction, supercurrent and superconducting order parameter as a function of the applied perpendicular magnetic field. We show that only in a restricted range of the magnetic field the vortex configuration obeys the geometry of the trench. Nevertheless, we clearly demonstrate that in our sample new phenomena are possible due to competing interactions of the geometry of the sample and the added geometry of the nanoengineered trench.

Structural, 99Ru Mossbauer, dc and ac susceptibility magnetization, and magneto-transport properties of the polycrystalline Eu2Ru2O7 pyrochlore are reported in this paper. From the experimental data, we deduce that the ruthenium cations Ru4+ (S = 1) are surrounded by an unusual electronic environment, involving conduction electron polarization and extrinsic Eu3+ ions at low temperature. This situation leads to an anomalous spin-glass transition at 23 K.

In this work, we present results on the structural, electrical, and magnetic properties of pure and half-doped LaCrO3 compounds. It is observed that including Mn the lattice structure changes from orthorhombic to rhombohedral. The electrical transport in LaCrO3 can be described by a band gap model, whereas in La2CrMnO6, a charge localization occurs and the electrical transport is described by a variable range hopping model. The magnetic measurements show that LaCrO3 is a G-type antiferromagnetic with a Neel temperature at 290 K, and the Mn doping favors the ferromagnetic order and reduces the transition temperature.

We study the synthesis and structural and magnetic characterization of the new compound family Sr2GdRu1−xRexOy, with doping levels at 3%, 6%, 9%, and 12%. X-ray diffractograms revealed that the samples crystallize in a monoclinic structure, and exhibit a strong distortion of the octahedron Ru(Re)O6/GdO6 lattice. Magnetic characterization revealed non-ideal antiferromagnetic behavior, with Neel temperatures close to 25 K, and an interesting metamagnetic feature below applied magnetic fields between 1.0 and 1.4 T. The existence of a Re doping level limit that favors an ideal antiferromagnetic character of the perovskite is discussed.

In this paper, we solve the Ginzburg–Landau equations for a circular geometry containing a half-circular pillar. We consider the surface of the sample in a complete normal state (|ψ| surface = 0), this choice, leading to take the extrapolation de Gennes length equal to zero (b = 0). Our results point out that the critical fields, magnetization and vorticity, depend on the chosen boundary condition.

We report reversible magnetization data and the scaling for the magnetization obtained for magnetic fields ( H ) applied at various tilt angles θ of the dc magnetic field with respect to the c axis in a single crystal of Bi 2 Sr 2 CaCu 2 O 8 . Our data show the crossover of the magnetization below the superconducting onset temperature, which indicates a dominant vortex fluctuation.

We report a crystallographic and magnetic characterization of the Sr2FeMnO6 novel polycrystalline complex manganite produced by the ceramic method. This material was mixed in volume percentages from 0% to 100% with the granular high temperature superconductor YBa2Cu3O7−δ to conform Sr2FeMnO6/YBa2Cu3O7−δ composites. Studies of chemical stability reveal that the Sr2FeMnO6 does not react with the YBa2Cu3O7−δ superconductor. X-ray results show an excellent coupling between the respective lattice parameters. DC susceptibility measurements indicate that the superconductivity of the YBa2Cu3O7−δ and the exotic magnetic properties of the Sr2FeMnO6 coexist up to 80% volume of this material in the composite. These characteristics permit to infer that these compounds would be utilized to the production of antiferromagnetic-superconductor multi-layer devices.

We report on the influence of a circular defect on the vortex configuration in a mesoscopic superconducting sample. Effects associated with the pinning force of the circular defect on the configuration and on the vortex entry fields are studied for a very thin disk. We calculate the magnetization loop, vorticity, free energy and superconducting electrons for the disk in presence of an external magnetic field applied perpendicular to the disk plane. The magnetization curves are hysteretic, with paramagnetic response in part of the downward branch, also, in this part we found a vortex–anti-vortex state.

Flux penetration and vortex patterns in narrow superconducting strips are studied. The edge barrier, vortex–vortex interactions, and the position dependent effective flux are calculated assuming the high-κ limit and strip width ξ≪W≪Λ, where Λ is the effective penetration depth and ξ the coherence length. Vortex penetration and time-evolution inside the sample, as an external magnetic field is looped, are simulated by numerically solving the coupled Langevin equations of motion. The edge barrier shows to have an important role on the system dynamics, producing metastable vortex-chain states.

The magnetic response of superconductors with a semicircular indentation in parallel field is studied. The indentation is placed in a long superconductor wedge. The Meissner and vortex fields are calculated for any indentation radius in the London background. This allowed us to obtain the energy and the forces acting on a vortex in a given position inside the superconductor. The entrance magnetic field dependence on the indentation radius is calculated and compared with the entrance field for an indentation free semi-infinite superconductor. The role of the indentation on the surface barrier and on the vortex dynamics is also discussed.

Two different series of ruthenium pyrochlores with the compositions Eu2−xCaxRu2O7 (0 ≤ x ≤ 0.6) and Eu2Ru2−xRexO7 (0 ≤ x ≤ 0.4) were prepared via solid state reaction, and their transport and magnetic properties were investigated. In both systems, the resistivity is shifted from 106 Ω cm to 10−3 Ω cm at low temperatures with increasing doping. The series correspond to two different approaches for inducing a metal–insulator transition in the Eu2Ru2O7 parent compound: (i) the substitution of Eu3+ by Ca2+, resulting in hole creation within the Ru t2g bands, and (ii) the partial substitution of Ru4+ (4d4) by Re4+ (5d3), leading to hole creation and an increase in the orbital overlap. Increasing the Ca or Re concentration suppresses the anomalies observed for Eu2Ru2O7 in dc magnetic susceptibility under zero-field-cooled and field-cooled conditions at 118 K and 23 K. In addition, a small negative magnetoresistance was obtained at low temperatures for doped samples with 2% Ca and Re.