Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.
School of Science, Tianjin University , Tianjin 300072, China.
ACS Appl Mater Interfaces. 2017 May 10;9(18):15644-15651. doi: 10.1021/acsami.7b02804. Epub 2017 Apr 28.
In this work, both negative and positive magnetoresistance (MR) in solution-processed regioregular poly(3-hexylthiophene) (RR-P3HT) is observed in organic spin valves (OSVs) with vertical LaSrMnO (LSMO)/P3HT/AlO/Co configuration. The ferromagnetic (FM) LSMO electrode with near-atomic flatness is fabricated by a DC facing-target magnetron sputtering method. This research is focused on the origin of the MR inversion. Two types of devices are investigated in details: One with Co penetration shows a negative MR of 0.2%, while the other well-defined device with a nonlinear behavior has a positive MR of 15.6%. The MR measurements in LSMO/AlO/Co and LSMO/Co junctions are carried to exclude the interference of insulating layer and two FM electrodes themselves. By examining the Co thicknesses and their corresponding magnetic hysteresis loops, a spin-dependent hybrid-interface-state model by Co penetration is induced to explain the MR sign inversion. These results proven by density functional theory (DFT) calculations may shed light on the controllable interfacial properties in designing novel OSV devices.
在这项工作中，通过具有垂直 LaSrMnO（LSMO）/P3HT/AlO/Co 结构的有机自旋阀（OSV），观察到溶液处理的规则排列聚（3-己基噻吩）（RR-P3HT）中的负磁阻（MR）和正磁阻（MR）。通过直流面对靶磁控溅射方法制备了具有近乎原子级平整度的铁磁（FM）LSMO 电极。这项研究集中于 MR 反转的起源。详细研究了两种类型的器件：一种具有 Co 穿透的器件表现出 0.2%的负 MR，而另一种具有非线性行为的良好定义器件则具有 15.6%的正 MR。在 LSMO/AlO/Co 和 LSMO/Co 结中进行了 MR 测量，以排除绝缘层和两个 FM 电极本身的干扰。通过检查 Co 厚度及其相应的磁滞回线，引入了一个由 Co 穿透引起的具有自旋依赖性的混合界面态模型，以解释 MR 符号反转。这些通过密度泛函理论（DFT）计算证明的结果可能为设计新型 OSV 器件中可控的界面性质提供了思路。
