Kwon Joon-Hyun, Kwak Won-Young, Cho Beong Ki
School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea.
Sci Rep. 2018 Oct 25;8(1):15765. doi: 10.1038/s41598-018-34036-z.
Spin-based electronic devices on polymer substrates have been intensively investigated because of several advantages in terms of weight, thickness, and flexibility, compared to rigid substrates. So far, most studies have focused on maintaining the functionality of devices with minimum degradation against mechanical deformation, as induced by stretching and bending of flexible devices. Here, we applied repetitive bending stress on a flexible magnetic layer and a spin-valve structure composed of Ta/NiFe/CoFe/Cu/Ni/IrMn/Ta on a polyimide (PI) substrate. It is found that the anisotropy can be enhanced or weakened depending upon the magnetostrictive properties under stress. In the flat state after bending, due to residual compressive stress, the magnetic anisotropy of the positive magnetostrictive free layer is weakened while that of the pinned layer with negative magnetostriction is enhanced. Thus, the magnetic configuration of the spin-valve is appropriate for use as a sensor. Through the bending process, we design a prototype magnetic sensor cell array and successfully show a sensing capability by detecting magnetic microbeads. This attempt demonstrates that appropriate control of stress, induced by repetitive bending of flexible magnetic layers, can be effectively used to modify the magnetic configurations for the magnetic sensor.
与刚性基板相比，基于聚合物基板的自旋电子器件因其在重量、厚度和柔韧性方面的诸多优势而受到广泛研究。到目前为止，大多数研究都集中在保持器件功能，使其在柔性器件拉伸和弯曲引起的机械变形下的降解最小。在此，我们对聚酰亚胺（PI）基板上由Ta/NiFe/CoFe/Cu/Ni/IrMn/Ta组成的柔性磁性层和自旋阀结构施加重复弯曲应力。结果发现，根据应力下的磁致伸缩特性，各向异性可以增强或减弱。在弯曲后的平坦状态下，由于残余压应力，正磁致伸缩自由层的磁各向异性减弱，而具有负磁致伸缩的钉扎层的磁各向异性增强。因此，自旋阀的磁结构适合用作传感器。通过弯曲过程，我们设计了一个原型磁传感器单元阵列，并通过检测磁微珠成功展示了传感能力。这一尝试表明，通过对柔性磁性层的重复弯曲所产生的应力进行适当控制，可以有效地用于修改磁传感器的磁结构。
