Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
Phys Rev Lett. 2013 Apr 26;110(17):177001. doi: 10.1103/PhysRevLett.110.177001. Epub 2013 Apr 24.
Magnetization noncollinearity in ferromagnet-superconductor (F/S) heterostructures is expected to enhance the superconducting transition temperature (T(c)) according to the domain-wall superconductivity theory, or to suppress T(c) when spin-triplet Cooper pairs are explicitly considered. We study the proximity effect in F/S structures where the F layer is a Sm-Co/Py exchange-spring bilayer and the S layer is Nb. The exchange-spring contains a single, controllable and quantifiable domain wall in the Py layer. We observe an enhancement of superconductivity that is nonmonotonic as the Py domain wall is increasingly twisted via rotating a magnetic field, different from theoretical predictions. We have excluded magnetic fields and vortex motion as the source of the nonmonotonic behavior. This unanticipated proximity behavior suggests that new physics is yet to be captured in the theoretical treatments of F/S systems containing noncollinear magnetization.
在铁磁体-超导体（F/S）异质结构中，磁化非共线有望根据畴壁超导理论提高超导转变温度（T(c)），或者在明确考虑自旋三重态库珀对时抑制 T(c)。我们研究了 F/S 结构中的近邻效应，其中 F 层是 Sm-Co/Py 交换弹簧双层，S 层是 Nb。交换弹簧在 Py 层中包含一个单一、可控且可量化的畴壁。我们观察到超导性增强是非单调的，因为通过旋转磁场，Py 畴壁越来越扭曲，这与理论预测不同。我们已经排除了磁场和涡旋运动是这种非单调行为的来源。这种出乎意料的近邻行为表明，在包含非共线磁化的 F/S 系统的理论处理中，仍有待捕捉新的物理现象。
