Long-ranged magnetic proximity effects in noble metal-doped cobalt probed with spin-dependent tunnelling
Long-ranged magnetic proximity effects in noble metal-doped cobalt probed with spin-dependent tunnelling
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DOI：
10.1088/1367-2630/16/4/043008
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发表时间：
2014-04
影响因子：
3.3
通讯作者：
M. Gabureac;D. Maclaren;H. Courtois;C. Marrows
中科院分区：
文献类型：
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作者：
M. Gabureac;D. Maclaren;H. Courtois;C. Marrows
我们插入非磁性层的Au和Cu溅射AlOx？>的磁性隧道结和Meservey-Tedrow结，以研究它们对隧道磁电阻（TMR）和自旋极化（TSP）的影响。当Au或Cu插入Co/AlOx？界面，我们发现TMR和TSP仍然是有限和可测量的厚度高达几个纳米。高分辨透射电子显微镜显示，当Cu和Au界面层的厚度超过103 nm时，它们是完全连续的。这意味着自旋极化载流子穿透界面贵金属的距离超过该值。一个幂律模型的基础上交换散射发现，以适应数据比现象学指数衰减。这些长度尺度之间的差异和短得多的报道从X射线磁性圆二色性研究磁proximitization归因于这样一个事实，即我们的隧道传输测量选择性地探测类s电子接近费米能级。当在Co中插入0.1 nm厚的Cu或Au层时，我们发现TMR和TSP的抑制在0.1 nm？>表明这是足够量的Co以在与隧道势垒的界面处形成完全自旋极化的能带结构。
We inserted non-magnetic layers of Au and Cu into sputtered AlO x ?> -based magnetic tunnel junctions and Meservey–Tedrow junctions in order to study their effect on tunnelling magnetoresistance (TMR) and spin polarization (TSP). When either Au or Cu are inserted into a Co/AlO x ?> interface, we find that TMR and TSP remain finite and measurable for thicknesses up to several nanometres. High-resolution transmission electron microscopy shows that the Cu and Au interface layers are fully continuous when their thickness exceeds ∼ 3 nm ?> , implying that spin-polarized carriers penetrate the interface noble metal to distances exceeding this value. A power law model based on exchange scattering is found to fit the data better than a phenomenological exponential decay. The discrepancy between these length scales and the much shorter ones reported from x-ray magnetic circular dichroism studies of magnetic proximitization is ascribed to the fact that our tunnelling transport measurements selectively probe s-like electrons close to the Fermi level. When a 0.1 nm thick Cu or Au layer is inserted within the Co, we find that the suppression of TMR and TSP is restored on a length scale of ⪅ 1 nm ?> , indicating that this is a sufficient quantity of Co to form a fully spin-polarized band structure at the interface with the tunnel barrier.