High quality ferromagnetic 0 and π Josephson tunnel junctions
High quality ferromagnetic 0 and π Josephson tunnel junctions
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高品质铁磁 0 和 π 约瑟夫森隧道结
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
A. Buzdin
中科院分区：
文献类型：
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作者：
M. Weides;M. Kemmler;E. Goldobin;D. Koelle;R. Kleiner;H. Kohlstedt;A. Buzdin
作者制造了高质量的 Nb∕Al2O3∕Ni0.6Cu0.4∕Nb 超导体-绝缘体铁磁体-超导体约瑟夫森隧道结。根据铁磁 Ni0.6Cu0.4 层的厚度和环境温度，结处于 0 或 π 基态。所有连接点都具有均匀的界面，显示出几乎完美的夫琅和费图案。 Al2O3 隧道势垒允许人们实现相当低的阻尼，这是许多实验尤其是在量子域中的实验所需要的。 McCumber 参数 βc 随着温度的降低呈指数增加，并在 T=2.11K 时达到 βc≈700。 T=2.11K时π态的临界电流密度高达5A/cm2，约瑟夫森穿透深度λJ低至160μm。考虑到 Ni0.6Cu0.4 层中的自旋翻转散射和界面的不同透明度，实验确定的结参数可以通过理论得到很好的描述。
The authors fabricated high quality Nb∕Al2O3∕Ni0.6Cu0.4∕Nb superconductor-insulatorferromagnet-superconductor Josephson tunnel junctions. Depending on the thickness of the ferromagnetic Ni0.6Cu0.4 layer and on the ambient temperature, the junctions were in the 0 or π ground state. All junctions have homogeneous interfaces showing almost perfect Fraunhofer patterns. The Al2O3 tunnel barrier allows one to achieve rather low damping, which is desired for many experiments especially in the quantum domain. The McCumber parameter βc increases exponentially with decreasing temperature and reaches βc≈700 at T=2.11K. The critical current density in the π state was up to 5A∕cm2 at T=2.11K, resulting in a Josephson penetration depth λJ as low as 160μm. Experimentally determined junction parameters are well described by theory taking into account spin-flip scattering in the Ni0.6Cu0.4 layer and different transparencies of the interfaces.