Granular superconductivity in polycrystalline ruthenocuprate RuSr2 (Gd1.5Ce0.5)Cu2O10- δ : magnetoresistive and magnetization studies

摘要: Granular superconductivity effects in polycrystalline samples of RuSr2(Gd1.5Ce0.5)Cu2O10??, as prepared (by a solid-state reaction method) and annealed (12?h at 845??C) pure oxygen 30?atm, are presented. The resistive transition to the superconducting state as-prepared sample is found be considerably affected by granularity. In particular, an evident kink temperature dependence resistance R(T) seen temperature, Tc0?34?K, which grains become superconducting. depends strongly on applied current. family curves taken for different transport currents branched with branching point TcJ?23.2?K. Below this intergrain Josephson coupling starts develop. For low current, R decreases decreasing below TcJ expected state, whereas higher current form minimum T?17.3?K, showing quasi-re-entrant behaviour. influence granular structure shows itself also behaviour magnetization, M(T), field. Application magnetic field (below 400?Oe) leads broadening transitions TcJ, similar that caused increasing Both depress between grains, producing dramatically large effect transition. M(T) dependences show fairly sharp far less results obtained imply annealing improves intergranular connection considerably, but it does not exert much intragrain superconductivity. No indication granularity has been studied. ageing (due deoxidation) conditions storage considered briefly well.