Study of Unconventional Triplet Superconductivity and Spin-Valve Effects in Superconductor/Ferromagnet Nanolayered Heterostructures

超导/铁磁体纳米层异质结构中非常规三重态超导和自旋阀效应的研究

• 批准号: 252046394
• 负责人: Professor Dr. Siegfried Rüdiger Horn
• 金额: --
• 依托单位: Institut für Materials Resource Management
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/252046394?language=en
• 关键词: Study; Unconventional; Triplet; Superconductivity; Spin

In heterostructures of a superconducting (S) and two ferromagnetic (F1,F2) nanolayers an odd in frequency s-wave triplet pairing generation occurs for a non-collinear orientation of the magnetizations (M1, M2) of the F-layers. This pairing channel is of extraordinary long range in the F-layers, because the equal-spin pairing is supported by the magnetized conduction band of the F-metal. The generation of this component significantly affects the transition temperature of both superconducting proximity effect spin-valve designs, F1/S/F2 and S/F1/F2. For the S/F1/F2 system the theory predicts an absolute minimum of the superconducting transition temperature close to the crossed configuration of M1 and M2. This effect is expected to be large (of order 1K between different alignments of the magnetizations) if the F-layers are magnetic alloys. Especially for these materials, we want to investigate the phenomenon in the present work and compare it with the corresponding phenomenon in F1/S/F2 structures. However, exchange biasing of a layer made of a diluted ferromagnetic alloy is a difficult task. Therefore, our recently improved method to exchange bias one of the ferromagnetic layers (especially important for a diluted ferromagnetic alloy) will be applied. In this way we also want to realize a large standard (or inverse) spin-valve effect of order 1K, as expected for the difference in the critical temperatures between parallel and antiparallel alignment of the magnetizations, for which the odd in frequency s-wave triplet pairing generation is not present. Moreover, we expect to solve the long-standing problem to distinguish the spin-valve effects from magnetic stray-field effects. To study the mutual influence of triplet components and the current transport in our systems, the spin-valve effects will be investigated at different applied magnetic fields and currents up to the critical one. Since our recent experiments on memory effects in a F/S/F type spin valve structure have shown evidence of non-equilibrium effects, we finally want to perform a pilot study on non-equilibrium superconductivity in S-F-heterostructures.

在超导（S）和两个铁磁（F1，F2）纳米层的异质结构中，频率s波三联成配对的奇数发生在f-layers的磁化（M1，M2）的非共线方向发生。该配对通道在F层中具有非凡的远距离，因为相等的自旋配对由F-Metal的磁化导带支持。该成分的产生显着影响超导接近效应自旋阀设计，F1/S/F2和S/F1/F2的过渡温度。 对于S/F1/F2系统，该理论预测了超导过渡温度接近M1和M2的交叉配置的绝对最小值。如果F层是磁合金，则预计这种效果将很大（磁化不同对齐之间的1K）。特别是对于这些材料，我们希望研究当前工作中的现象，并将其与F1/S/F2结构中的相应现象进行比较。但是，交换由稀释的铁磁合金制成的层是一项艰巨的任务。 因此，将应用我们最近改进的交换偏见的方法之一（对于稀释的铁磁合金尤其重要）。 通过这种方式，我们还希望实现1K阶的大标准（或逆）自旋阀效应，这是预期的，这对于磁化的并联和反平行比对之间的临界温度的差异所预期，而频率s-wave三胞胎配对中的奇数不存在。 此外，我们希望解决长期存在的问题，以区分自旋阀效应与磁性杂散场效应。 为了研究三元组成分和系统中当前运输的相互影响，将在不同的施加磁场和电流之前研究自旋阀效应。 由于我们最近对F/S/F型自旋阀结构中记忆效应的实验表明了非平衡效应的证据，因此我们最终希望对S-F型型结构中的非平衡超导性进行试验研究。