Reconfigurable superconducting vortex pinning potential for magnetic disks in hybrid structures.
Reconfigurable superconducting vortex pinning potential for magnetic disks in hybrid structures.
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DOI：
10.1038/srep45182
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发表时间：
2017-03-24
影响因子：
4.6
通讯作者：
Bending SJ
中科院分区：
文献类型：
--
作者：
Marchiori E;Curran PJ;Kim J;Satchell N;Burnell G;Bending SJ
高分辨率扫描霍尔探针显微镜被用来直接观察由微米大小的Py铁磁磁盘组成的方形阵列组成的混合结构中的超导涡旋行为，该阵列由超导Nb薄膜覆盖。在剩磁状态下，磁盘几乎处于完全磁通闭合的磁旋涡状态，但观测到的类似三叶草的杂散场表明存在较弱的面内各向异性。微磁模拟表明，最有可能的起源是无意的形状各向异性。我们研究了附加自由超导涡旋的钉扎作为磁盘磁化状态的函数，并发现了一系列不同的现象，这些现象是由竞争的能量贡献引起的。我们还观察到，当超导体和铁磁体被电子耦合或由薄的电介质层绝缘时，钉扎情况明显不同，表明存在非平凡的涡旋-涡旋相互作用。我们证明了在面内磁场作用下，当圆盘的磁化从类涡旋状态演化为类洋葱状态时，涡旋钉扎势的完全重构。我们的结果与理论预测很好地符合，可以为基于可重构涡钉扎位的新型超导器件奠定基础。
High resolution scanning Hall probe microscopy has been used to directly visualise the superconducting vortex behavior in hybrid structures consisting of a square array of micrometer-sized Py ferromagnetic disks covered by a superconducting Nb thin film. At remanence the disks exist in almost fully flux-closed magnetic vortex states, but the observed cloverleaf-like stray fields indicate the presence of weak in-plane anisotropy. Micromagnetic simulations suggest that the most likely origin is an unintentional shape anisotropy. We have studied the pinning of added free superconducting vortices as a function of the magnetisation state of the disks, and identified a range of different phenomena arising from competing energy contributions. We have also observed clear differences in the pinning landscape when the superconductor and the ferromagnet are electron ically coupled or insulated by a thin dielectric layer, with an indication of non-trivial vortex-vortex interactions. We demonstrate a complete reconfiguration of the vortex pinning potential when the magnetisation of the disks evolves from the vortex-like state to an onion-like one under an in-plane magnetic field. Our results are in good qualitative agreement with theoretical predictions and could form the basis of novel superconducting devices based on reconfigurable vortex pinning sites.