Abstract

Nanowires of different types (homogeneous (made of iron) and heterogeneous (layered)), obtained by the template synthesis method, have been investigated. A technique for preparation of layered nanowire arrays with alternating thin layers of magnetic and nonmagnetic metals (Co/Cu and Ni/Cu) has been developed and described. Microscopy methods (SEM and TEM with elemental analysis) are used to study topography of the obtained structures, nanowire diameters, individual-layer thicknesses, and specific features of layer interfaces. Several ways of synthesis of nanowires with thin layers and sharp interfaces are proposed: dilution of electrolyte, use of a reference electrode, and monitoring of the charge passage. Layered nanowires are investigated by magnetometry; it is shown that the magnetic properties of a layered nanowire array (in particular, direction of the easy magnetization axis in the Co/Cu nanowire array) depend not only on the aspect ratio of the magnetic layer but also on the thickness ratio between the magnetic-metal layer and the nonmagnetic spacer (copper interlayer). Nanowires of the two types are studied using the nuclear magnetic resonance (NMR) method. Layered Co/Cu structures are analyzed by ⁵⁹Co NMR: it is shown that nanowires with smaller-thickness layers (and, accordingly, with a larger contribution from the interfaces) are characterized by a larger fraction of Co atoms coordinated by Cu atoms. The large fraction of the Cu-coordinated atoms suggests that copper impurity enters cobalt layers. Homogeneous nanowires made of iron are compared with bulk iron samples (⁵⁷Fe NMR). The line is found to be shifted to higher frequencies (by 0.3 MHz), which is indicative of an increase in the field by about 0.2 T. A significant line broadening and a decrease in the spin–lattice relaxation time may indicate that there is a large dispersion between the local magnetic field values.

中文翻译：

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不同类型纳米线的合成、结构、磁力测量和核磁共振光谱的具体特征

摘要

已经研究了通过模板合成方法获得的不同类型（均质（由铁制成）和异质（分层））的纳米线。已经开发和描述了一种制备具有磁性和非磁性金属（Co/Cu 和 Ni/Cu）的交替薄层的分层纳米线阵列的技术。显微镜方法（SEM 和 TEM 与元素分析）用于研究获得的结构的形貌、纳米线直径、单层厚度和层界面的特定特征。提出了几种合成具有薄层和尖锐界面的纳米线的方法：稀释电解质、使用参比电极和监测电荷通道。层状纳米线通过磁力计进行研究；结果表明，层状纳米线阵列的磁性（特别是，Co/Cu纳米线阵列中易磁化轴的方向）不仅取决于磁性层的纵横比，还取决于磁性金属层和非磁性间隔物（铜夹层）之间的厚度比。使用核磁共振（NMR）方法研究这两种类型的纳米线。层状 Co/Cu 结构通过以下方式分析⁵⁹ Co NMR：表明具有较小厚度层的纳米线（并且因此具有较大的界面贡献）的特征在于较大比例的Co原子与Cu原子配位。大部分铜配位原子表明铜杂质进入钴层。将由铁制成的均质纳米线与块状铁样品（⁵⁷ Fe NMR）进行比较。发现该线移动到更高的频率（0.3 MHz），这表明场增加了约 0.2 T。显着的线展宽和自旋晶格弛豫时间的减少可能表明存在局部磁场值之间的大分散。