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In order to explore the possibility of tuning superconducting and ferromagnetic transitions by Cu doping (for Ru) in GdSr2RuCu2O8, we have carried out synthesis and characterization of GdSr2Ru1−xCu2+xO8 (x = 0, 0.05, 0.1, 0.2) and studied their physical properties. Coexistence of superconductivity and ferromagnetism is observed in all the Cu doped samples studied here. The zero field susceptibility data suggests formation of a spontaneous vortex phase. Cu doping decreases the ferromagnetic Curie temperature, whereas the superconducting transition temperature increases until an optimal concentration x ∼0.1. This reflects an increase in hole transfer to the CuO2 planes and reduction of ferromagnetic order within the ruthenate layers.

Thin films of Fe1+δSe1−xTex (δ∼0.18 and x∼0.5) have been successfully grown on (100)-oriented single-crystalline SrTiO3 and LaAlO3 substrates by pulsed laser deposition. The crystal structure was characterized by x-ray diffraction and the superconducting properties by electrical resistivity measurements. X-ray diffraction analysis establishes the growth of films with c-axis orientation. Atomic force microscopy showed a smooth surface morphology for the films grown on SrTiO3 substrates. All the films are observed to be superconducting with a transition temperature, Tc of ∼8–14 K, depending on the deposition conditions. The deposition parameters were optimized to obtain good quality films with Tc comparable to that of the target material. The upper critical field shows a positive curvature near Tc unlike the opposite behavior observed in conventional superconductors.

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