RuSr₂Gd_1.5Ce_0.5Cu₂O_10-δ超伝導体の非線形磁化応答

抄録

We have investigated the magnetic response of superconductivity on the magnetic superconductor RuSr₂Gd_1.5Ce_0.5Cu₂O_10−δ. The high-quality polycrystalline sample was synthesized with the additional excess ruthenium. Superconductivity of the sample appears below 31 K. Fundamental and higher-harmonic complex susceptibilities χ_n=χ_n'−iχ_n'' were measured. For all n, χ_n appears below 26 K. The results suggest the sample magnetizes non-linearly to magnetic fields below the temperature. The magnetization curves at low magnetic fields were obtained by substituting observed χ_n in Fourier series of the time-dependent magnetization. The magnetization curve below 31 K indicates a hysteresisless diamagnetism. The diamagnetism is due to the intragrain superconductivity. The magnetization curve below 26 K indicates a hysteresis loop as the mixed state in type-II superconductors simultaneously with the hysteresisless diamagnetism. The hysteresis loop is due to the intergranular superconductivity. From the hysteresis width of the magnetization curve, the intergranular-critical current density was estimated at 7.5×10³A/m² on 5 K.