N. Balchev¹, K. Nenkov², J. Warchulska², Y. Skourski², V. Nizhankovskii², B. Kunev³, A. Souleva⁴, Ts. Tsacheva^5
1Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria
²Int. Laboratory of High Magnetic Fields and. Low Temperatures, 53-421 Wroclaw Poland
³Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
⁴University of Chemical Technology and Metallurgy, 1756 Sofia, Bulgaria
⁵Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Abstract. The effect of Sn-doping in (Pb,Cu)Sr₂(Y_0.6Ca_0.4)Cu₂O_z was investigated. The results of the XRD, 1CP-AES and EDX on SEM analyses showed that the obtained material contained the phase 1212. The EDX analysis in different points showed that tin was present in most of the microcrystals but its distribution was inhomogeneous. The resistivity and susceptibility measurements denoted superconductivity at T_e = 20 K. The dependence of the resistance on the magnetic field showed about 20% of magnetoresistance effect at 4.2 K, which coexisted with the superconducting state up to H = 1 k(E. The low values of T_c and the magnetoresistance were explained by assuming that a part of Sn occupied copper positions in the CuO₂ planes.

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