Superconductivity in the (Ga1-yCoy)Sr2(Tm1-xCax)Cu2Oz compounds synthesized under ambient pressure

초록

A search for superconductivity has been performed with (Ga0.5Co0.5)Sr-2(Tm(1-)xCa(x))Cu2Oz (0 <= x <= 0.5) and (Ga1-yCoy)Sr-2(Tm0.6Ca0.4)Cu2Oz (0 <= y <= 1.0) compounds synthesized tinder ambient pressure. Materials are characterized by X-ray diffraction, electrical transport, magnetic susceptibility measurements. The X-ray diffraction pattern reveals that all samples have in orthorhombic Ima2 structure. We find that the Co substitution for Ga results in all increase of the solubility limit of Ca of GaSr2(Tm1-xCax)Cu2Oz, and thereby superconductivity is induced by the co-substitution of Ca for Tm and Co for Ga. Bulk superconductivity with a T-c of 35 K is observed in a sample with nominal composition of (Ga0.5Ca0.5)Sr-2(Tm0.6Ca0.4)Cu2Oz. The variation of the room-temperature thermoelectric power shows that the carrier concentration on the superconducting planes is sensitive to the substitution of Co for Ga in addition to the Ca substitution for Tm. (c) 2005 Elsevier B.V. All rights reserved.

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