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In this paper, we present experimental research on the crystal structure, morphology, and magnetic properties of the Nd3Ba5Cu8O18+ẟ superconductor. The powder sample was obtained through the standard solid-state reaction at a temperature of 850 °C in oxygen atmosphere. Using the X-ray diffraction technique (XRD), the phase content of the calcined powder was investigated. A Rietveld refinement of XRD patterns shows that the material crystallizes in an orthorhombic structure, which belongs to Pmm2 (25) space group, with lattice parameters a = 3.914(3) Å, b = 3.880(3) Å, and c = 31.288(8) Å. Scanning electron microscopy (SEM) shows a granular formation for the sample and the elementary composition. Magnetization curves as a function of temperature were obtained for the first time using the vibrating sample magnetometry technique (VSM) in a zero field cooled/field cooled (ZFC/FC) mode to calculate the critical temperature (Tc) and irreversibility temperature (Tirr). The measurements reveal a superconductor behavior with a Tc = 78.09 K and a Tirr = 72.01 K. [ABSTRACT FROM AUTHOR]

The present study reports the structural, magnetic and electrical properties of the $$\hbox {Na}_{0.5}\hbox {CoO}_{3}$$ system produced by the conventional solid state reaction method. The X-ray diffraction analysis allows to infer that the compound crystallizes in a monoclinic system with spatial group $$\textit{C2/m}$$ and network parameters: $$a = 5.55$$ (8) Å, $$b = 4.87$$ (3) Å y $$c = 2.85$$ (8) Å. It is found that the mean grain size of the stoichiometric of system amounts approximately to 76 nm. Below 40 K, an antiferromagnetic behavior with $${T}_{N }\approx $$ 40 K was observed, while in the region between 80 and 190 K the system obeys the law of Curie-Weiss, and the effective magnetic moment was determined experimentally of $$5.62{\mu }_{B}$$ , indicating a high spin configuration for the $$\hbox {Co}^{2+ }$$ ion ( S = 3/2) in the fundamental state $$^{4}T_{1g}$$ . The system shows cluster spin glass properties with low temperatures, the temperature of magnetic moment freezing from $$\sim \,40\,\hbox {K}$$ . The behavior of the resistivity under absence of magnetic field and the presence of an insulating state between two different metallic states was observed. The metal-insulator transition occurred at two temperatures, the first around 170 K, and the second around 40 K, the latter in accordance with the magnetic transition temperature. [ABSTRACT FROM AUTHOR]

This paper reports the production of YBa $$_{2}$$ Cu $$_{3-x}$$ Fe $$_{x}$$ O $$_{7-\delta }$$ (0.05 $$\le x$$ $$\le $$ 0.12) superconducting system by using the standard solid-state reaction technique. A Rietveld refinement of the experimental X-ray diffraction patterns allows the determination of the lattice parameters and the phase composition of the studied system; the mean present phase shown is an orthorhombic phase Pmmm. Magnetic and transport properties are typical for superconducting samples. In this paper, magnetic susceptibility fluctuations are studied in the limit of weak magnetic fields. For each of the samples, the best fit of the experimental data of $$\Delta \chi $$ /T, in the limit of weak magnetic fields in function of the reduced temperature, allowed us to obtain the values of $$A_\mathrm{s}$$ (diamagnetism of Schmidt) and $$B_\mathrm{LD}$$ (LD parameter). The Lawrence-Doniach model (LD) has been used for the fluctuation analysis. It is demonstrated, by means of the analysis of the thermal fluctuations, that the YBa $$_{2}$$ Cu $$_{3-x}$$ Fe $$_{x}$$ O $$_{7-\delta }$$ system has an excellent 2D scaling behavior (BLD). [ABSTRACT FROM AUTHOR]