Direct Measurement of Spin Polarization in Ferromagnetic-C60 Interfaces Using Point-Contact Andreev Reflection
Direct Measurement of Spin Polarization in Ferromagnetic-C60 Interfaces Using Point-Contact Andreev Reflection
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DOI：
10.1109/tmag.2014.2322658
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发表时间：
2014-11-01
影响因子：
2.1
通讯作者：
Cespedes, Oscar
中科院分区：
文献类型：
--
作者：
Al Ma'Mari, Fatma;Wheeler, May;Cespedes, Oscar
将自旋电子学与有机电子学的潜力结合起来，是分子自旋电子学发展的重要一步，与无机器件相比，分子自旋电子学具有更大的灵活性、更高的可回收性和更低的生产成本。结构为Co(20 Nm)/Al-2O-3(1.2 nm)/C-60(5-60 nm)/Py(20 Nm)/Al(1.5 nm)的C-60自旋阀的室温磁阻(MR)为5%。在低温下，我们观察到磁流变场与电压的不对称依赖关系，并且令人惊讶的是，与磁场的依赖关系也是如此。这种行为归因于在结点处形成的有机界面，这导致了铁磁体的自旋极化的变化。通过测量金属-超导点接触电导的偏置依赖关系，提取了有机-铁磁界面处的自旋极化，并用改进的Blonder-Tinkham-Klip wijk理论分析了谱。点接触Andreev反射测量表明，Co-C-60的自旋极化为30%+/-1%，而不含C-60的Co薄膜的自旋极化为40%+/-1%。这可能解释了含有C-60的自旋阀中MR的不对称性以及需要氧化铝间隔来最大化MR的原因。
An important step has been developed combining the potential of spintronics with organic electronics to reveal the promising field of molecular spintronics, which can offer more flexibility, higher recyclability, and low-production costs compared with inorganic devices. Room temperature magnetoresistance (MR) of 5% has been obtained from C-60 spin valves with the structure Co(20 nm)/Al-2 O-3(1.2 nm)/C-60 (5-60 nm)/Py(20 nm)/Al(1.5 nm). We observe an asymmetric dependence at low temperatures of the MR with voltage, and surprisingly with the magnetic field as well. This behavior has been attributed to the organic interface formed at the junction, which results in a change of the ferromagnet's spin polarization. The spin polarization at the organic-ferromagnetic interface is extracted by measuring the bias dependence of the conductance of a metallic-superconducting point contact and analyzed the spectra with the modified Blonder-Tinkham-Klapwijk theory. Point-contact Andreev reflection measurements reveal that the Co-C-60 possess spin polarization of 30% +/- 1%, compared with 40% +/- 1% for our Co films without C-60. This could account for the asymmetry of the MR in spin valves incorporating C-60 and the need for an alumina spacer to maximize the MR.