Magnetic field-dependent resistance measurements in the superconducting ferromagnet (Ru1-xNbx)Sr2Eu1.4Ce0.6Cu2O10

Polycrystalline samples of Ru1-xNbxSr2Eu1.4Ce0.6Cu2O10-delta(x = 0, 0.2, 0.4, 0.6, 0.8,1) were prepared by conventional solid state reaction using stoichiometric amounts of high purity RuO2, Nb2O5, SrCO3, Eu2O3, CeO2, and CuO powders. The phase evolution during the solid state reaction was followed by x-ray diffraction and randomly oriented particles in laminates form with a size between 1-3 mu m were observed by scanning electron microscopy. Temperature-dependent resistance measurements were made with applied magnetic fields of 0, 2, 5, 10, and 15 T. All compositions except x = 1 were superconducting without applied magnetic field for the lowest measuring temperatures. Onset, intergrain and intragrain transition, and T-R=0 transition temperatures were determined. These critical temperatures depend on Nb content, microstructure, and applied magnetic field. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3070616]