Fabrication of high-Tc Junction using long range proximity effect

该项目的目的是1）弄清楚在使用钙钛矿锰氧化物作为阻挡层的结中发现的所谓的长程邻近效应是否是真实的。2)利用这些势垒来制造高性能的约瑟夫森结，以及3）研究钙钛矿Mn氧化物的物理性质。1）在PLD方法中，用非常少量的液滴来制造薄膜是至关重要的。我们尝试使用所谓的日食方法制造，并实现了液滴的急剧减少。在这项研究中，我们不能将这种方法应用于制造结，但计划在未来这样做，以实现目标1）和2）。对于3），我们制备了Nd（0.5）Ba（0.5）MnO（3-x）、Y（0.5）Ba（0.5）MnO（3-x）和La（1-z）Ba（y）Ca（z-y）MnO（3-x）的薄膜。我们制作了表面相当平坦的良好薄膜。在未来，我们将使用这些材料作为屏障。在La（1-z）Ba（y）Ca（z-y）MnO（3-x）薄膜中发现了一种非常反常的行为。在La（1-z）Ca（z）MnO（3-x）中加入Ba后，薄膜在低温下表现出绝缘体到金属的转变，但其磁电阻却表现出很大的反常。在Pr（0.5）Ca（0.5）MnO（3-x）薄膜中，我们观察到与单晶体一样，在外加电场作用下，薄膜的电阻显著降低。

The aims of this project are 1) to make clear whether the so-called, long range proximity effect found in junctions using perovskite Mn oxides as a barrier, is real or not., 2) to fabricate high performance Josephson junctions using these barriers, and 3) to investigate physical properties of perovskite Mn oxides.To 1), fabrication of thin films with a very small number of droplets inherent in the PLD method is crucial. We tried fabrication using the so-called eclipse method and attained drastic decrease of droplets. In this research, we could not apply this method in fabricating junctions, but plan to do this in future to realize the aims 1) and 2). As to 3), we fabricated thin films of Nd(0.5)Ba(0.5)MnO(3-x), Y(0.5)Ba(0.5)MnO(3-x), and La(1-z)Ba(y)Ca(z-y)MnO(3-x). We fabricated good films with rather flat surface. In future, we use these materials as a barrier. We found a quite anomalous behavior in La(1-z)Ba(y)Ca(z-y)MnO(3-x) thin films. With addition of Ba to La(1-z)Ca(z)MnO(3-x), the film showed insulator to metal transition at low temperature, but, its magneto resistance turned out quite anomalous. It showed a positive magnetoresistance which is quite unusual in perovskite Mn oxides.In Pr(0.5)Ca(0.5)MnO(3-x) thin films, we observed strong decrease of the electrical resistance under application of external electric field as was found in single crystals.