Critical magnetic fields in the rutheno-cuprates Ru(1− x )Nb x Sr2Eu1.4Ce0.6Cu2O10

• Published in: Journal of applied physics 2012-04, Vol.111 (7)
• Main Authors: Botello-Zubiate, M. E., Matutes-Aquino, J. A., Ayala-Valenzuela, O. E., Jaime, M.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3676418

II-type superconducting rutheno-cuprates are both interesting and challenging systems where there is a coexistence of superconductivity and magnetism, so far poorly understood. The magnetic transitions that occur before the superconducting transition in Ru-1212 are simpler and better understood than those found in Ru-1222. In this work, polycrystalline Ru(1−x)NbxSr2Eu1.4Ce0.6Cu2O10 samples (Ru-1222) with x = 0, 0.2, 0.4, and 0.6, were prepared by conventional solid state reaction using stoichiometric amounts of high purity oxide powders: RuO2, Nb2O5, SrCO3, Eu2O3, CeO2, and CuO. The phases were identified by x-ray diffraction. From electrical resistance measurements as a function of the applied magnetic field at different temperatures (4 to 40 K), the Hc2 critical field or a lower limit of this was determined for each composition. At the lower measurement temperatures, from T = 4 K to T = 20 K, it was only possible to set a lower limit for the critical magnetic field, Hc2, of 140 kOe for compositions x = 0 and 0.2, while for compositions x = 0.4 and 0.6 the critical magnetic field, Hc2, were 110 and 84 kOe, respectively at T = 4 K. The dependence of these critical magnetic fields, Hc2, with temperature and composition is discussed.