Superconducting and Magnetic Properties of Polycrystalline [(Bi,Pb)2Sr2Ca2Cu3Ox]1−x(La0.7Sr0.3MnO3)x Thick Films Grown Using MQA Method

Polycrystalline thick films with the nominal composition [(Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O x ] 1− x (La 0.7 Sr 0.3 MnO 3 ) x ( x =0, 0.01, 0.03, 0.05) were prepared by the melting-quenching-annealing (MQA) method on (001)-oriented LaAlO 3 (LAO) substrates. The XRD patterns show that the samples are composites consisting of (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O x and La 0.7 Sr 0.3 MnO 3 particles with average grain sizes of ∼60 and ∼30 nm, respectively. From electric transport measurements, the superconducting onset temperature, T onset , and superconducting critical temperature, T c , ended up being ∼80 and ∼60 K, respectively. The depression of T c may be attributed to the proximity effect between ferromagnetism and superconductivity. The M – H hysteresis loops indicate the coexistence of ferromagnetism and superconductivity in the films. The magnetic field dependence of the superconducting current density and the volume pinning force F p = J c × B were obtained by applying Bean’s model to the isothermal M – H loops.