YBCO thin-film step-edge junctions have been prepared whose characteristics show features corresponding to the two tilt-angle grain-boundary junctions formed at the step. The I-V characteristics of these junctions are fitted to high accuracy by a model consisting of two noisy resistively-shunted Josephson junctions. In applied magnetic fields up to a few hundred microtesla, both junction critical currents show reversible flux modulation, in one case indicating excellent uniformity of the critical current distribution along the step. In stronger magnetic fields, the junction critical current modulation shows evidence of flux penetration into the film, i.e. the mixed state. Taking demagnetising effects into account the lower critical field of YBCO at 77 K, /spl mu//sub 0/H/sub e1,e/, is found to be 12 mT.
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机译：制备了YBCO薄膜台阶边缘结，其特征显示出与在该台阶处形成的两个倾斜角晶界结相对应的特征。这些结的I-V特性通过一个由两个嘈杂的电阻分流的约瑟夫森结组成的模型进行了高精度拟合。在高达数百微特斯拉的施加磁场中，两个结点的临界电流都显示出可逆的磁通调制，在一种情况下，表明沿阶跃方向的临界电流分布具有出色的均匀性。在更强的磁场中，结临界电流调制显示出磁通渗透到薄膜中的证据，即混合态。考虑到去磁作用，YBCO在77 K时的下临界磁场为/ spl mu // sub 0 / H / sub e1，e /，为12 mT。
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