Neumann R F, Bahiana M, Allende S, Altbir D, Görlitz D, Nielsch K
IBM Research, Av. Pasteur 138 & 146, Urca, Rio de Janeiro, CEP 22290-240, Brazil.
Nanotechnology. 2015 May 29;26(21):215701. doi: 10.1088/0957-4484/26/21/215701. Epub 2015 May 1.
The magnetization reversal of three-segment cylindrical nanoelements comprising alternating nanowire and nanotube sections is investigated by means of Monte Carlo simulations. Such nanoelements may feature a three-state behaviour with an intermediate plateau in the hysteresis curve due to a metastable pinning of the domain walls (DWs) at the wire-tube interfaces. It turns out that vortex as well as transverse DWs contribute to the magnetization reversal. By varying the geometric parameters, the sequence, or the material of the elements the nucleation location of DWs, as well as their nucleation field, can be tailored. Especially interesting is the novel possibility to drive DWs coherently in the same or in opposite directions by changing the geometry of the hybrid nanoelement. This important feature provides additional flexibility to the construction of logical devices based on DW movement. Another prominent outcome is that DWs can be nucleated near the centre of the element and then traverse to the outer tips of the cylindrical structure when the applied field is increased, which also opens the possibility to use these three-segment nanoelements for the field-induced delivery of DWs as substitutes for large nucleation pads.
通过蒙特卡罗模拟研究了由交替的纳米线和纳米管段组成的三段式圆柱形纳米元件的磁化反转。由于畴壁（DWs）在线-管界面处的亚稳态钉扎，这种纳米元件可能具有三态行为，磁滞曲线中有一个中间平台。结果表明，涡旋以及横向DWs都对磁化反转有贡献。通过改变元件的几何参数、序列或材料，可以调整DWs的成核位置及其成核场。特别有趣的是，通过改变混合纳米元件的几何形状，可以以相同或相反方向相干驱动DWs的新可能性。这一重要特性为基于DW运动的逻辑器件的构建提供了额外的灵活性。另一个显著结果是，当外加磁场增加时，DWs可以在元件中心附近成核，然后穿过圆柱形结构的外端，这也为使用这些三段式纳米元件进行场诱导的DWs传输以替代大型成核垫提供了可能性。
