Instituto de Ciencia de Materiales de Aragón, Facultad de Ciencias, Universidad de Zaragoza-CSIC, E-50009, Zaragoza, Spain.
Nanotechnology. 2013 Aug 30;24(34):345703. doi: 10.1088/0957-4484/24/34/345703. Epub 2013 Jul 30.
Applications based on the movement of domain walls (DWs) in magnetic nanowires (NWs) require a good DW conduit behavior, i.e. a significant difference between DW nucleation and propagation fields. In this work, we have systematically studied how this property evolves in cobalt NWs grown by focused electron beam induced deposition (FEBID) as a function of global gallium irradiation, for irradiation doses up to 1.24 × 10(17) ions cm(-2). Whereas for high doses the DW conduit is lost, below 6.42 × 10(15) ions cm(-2) the difference between the two fields increases with irradiation, becoming up to ∼9 times larger than for non-irradiated wires, due to a strong increase in the nucleation field, while the propagation field remains approximately constant. This behavior stems from two effects. The first effect is a decrease in the magnetic volume of the parasitic halo around the NW, typically present in FEBID nanostructures, leading to the disappearance of weak nucleation centers. The second effect is the formation of a 20 nm outer shell with Co crystals about twice the size of those forming the NW core, causing a net increase of the local magnetocrystalline anisotropy. The results presented here are important for the potential use of magnetic NWs grown by FEBID in DW-based devices, and might also be of interest for magnetic NWs fabricated by other techniques.
基于磁纳米线（NWs）中畴壁（DWs）运动的应用需要良好的 DW 输送行为，即 DW 成核和传播场之间有显著差异。在这项工作中，我们系统地研究了在聚焦电子束诱导沉积（FEBID）生长的钴 NWs 中，随着全局镓辐照的变化，这种性质如何演变，辐照剂量高达 1.24×10(17)ions cm(-2)。虽然高剂量会导致 DW 输送丧失，但在 6.42×10(15)ions cm(-2)以下，两个场之间的差异随辐照增加而增加，最大可达非辐照线的 9 倍，这是由于成核场的强烈增加，而传播场基本保持不变。这种行为源于两个效应。第一个效应是 NW 周围寄生晕环的磁体积减小，通常存在于 FEBID 纳米结构中，导致弱成核中心消失。第二个效应是形成一个 20nm 厚的外壳，外壳中的 Co 晶体大约是 NW 核心晶体的两倍大，导致局部磁各向异性净增加。这里呈现的结果对于 FEBID 生长的磁 NW 在基于 DW 的器件中的潜在应用很重要，对于其他技术制备的磁 NW 也可能有兴趣。
