Fabrication of high-Tc Junction using long range proximity effect

这个项目的目的是1)弄清楚所谓的，在使用钙钛矿锰氧化物作为屏障的结中发现的远距离接近效应是否真实。2)利用这些屏障制造高性能约瑟夫森结，以及3)研究钙钛矿Mn氧化物的物理性质。对于1)，在PLD方法中，具有非常少量液滴的薄膜的制造是至关重要的。我们尝试用所谓的“蚀法”制造，得到了液滴急剧减少的结果。在本研究中，我们不能将这种方法应用于制造连接，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）薄膜。我们制作了表面相当平坦的好薄膜。未来，我们将使用这些材料作为屏障。我们在La(1-z)Ba(y)Ca(z-y)MnO（3-x）薄膜中发现了相当反常的行为。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向金属的转变，但其磁电阻却出现了异常。它表现出正磁阻，这在钙钛矿锰氧化物中是很不寻常的。在Pr(0.5)Ca(0.5)MnO（3-x）薄膜中，我们观察到在外加电场的作用下，电阻与单晶一样有明显的下降。

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.