Proximity effect and electron transport in oxide hybrid heterostructures with superconducting/magnetic interfaces

摘要

We report on electron transport in oxide heterostructures with superconducting/magnetic (S/M) thin film interfaces. The investigated hybrid mesa-heterostructures consist of a cuprate superconductor, a nonsuperconducting cuprate (antiferromagnetic) or manganite (ferromagnetic) interlayer with thickness d_M = 5-50nm and a conventional superconductor (Nb). The superconducting critical current (I_C) with a critical current density j_c = 10~3Acm~(-2) (for d_M = 10nm) and a characteristic voltage I_CR_N = 100-200μV (R_N is normal resistance) are observed at liquid helium temperature for a Ca _XSr_(1-X)CuO_2 antiferromagnetic cuprate interlayer with a thickness of d_M = 10-50nm. The superconducting current-phase relation of heterostructures deviates from the regular sine type, demonstrating a second harmonic component. These hybrid heterostructures with S/M interfaces show unusually high sensitivity to external magnetic fields. When substituting the cuprate interlayer by a manganite film, no critical current was observed although the manganite interlayer was made several times thinner (down to d _M ≤ 5nm).