Various types of nanowires obtained by matrix synthesis --- homogeneous (from iron) and heterogeneous (layered) --- have been studied. A technique for obtaining arrays of layered nanowires with alternating thin layers of magnetic and non-magnetic metals (Co/Cu, Ni/Cu) has been developed and described. Microscopy methods (SEM and TEM with elemental analysis) have been used to study the topography of the resulting structures, the diameters of nanowires and the thicknesses of individual layers, and the features of interlayer interfaces. Methods of synthesis of nanowires with thin layers and clear boundaries are proposed --- dilution of the electrolyte, use of a reference electrode, control of the leaked charge. Layered nanowires have been studied by magnetometry methods and it has been shown that the magnetic properties of an array of layered nanowires (in particular, the direction of the axis of light magnetization in the Co/Cu-NP array) depend not only on the aspect ratio of the magnetic layer, but also on the ratio of the thickness of the magnetic metal layer to the thickness of a non-magnetic spacer (copper layer). The nuclear magnetic resonance (NMR) method was used to study two types of nanowires. The NMR method (on 59-Co nuclei) studied the layer structures of Co/Cu: it is shown that in nanowires with layers of smaller thickness (and, accordingly, with a large contribution of interfaces), a large proportion of Co atoms coordinated by Cu atoms is observed. The high proportion of atoms coordinated by copper suggests that an admixture of copper enters the cobalt layers. Homogeneous iron nanowires (NMR on 57-Fe nuclei) were compared with bulk iron samples. A shift of the line towards high frequencies (by 0.3 MHz) was detected, indicating an increase in the field by about 0.2 T. A significant broadening of the line and a decrease in the spin-lattice relaxation time may indicate a significant variation in the local magnetic field values. Keywords: nanowires, matrix synthesis, microscopy, elemental analysis, magnetic properties, NMR.

Исследованы различные типы нанопроволок, полученных методом матричного синтеза --- гомогенные (из железа) и гетерогенные (слоевые). Разработана и описана методика получения массивов слоевых нанопроволок, с чередующимися тонкими слоями магнитных и немагнитных металлов (Co/Cu, Ni/Cu). Методами микроскопии (СЭМ и ПЭМ с элементным анализом) изучена топография получаемых структур, диаметры нанопроволок и толщины отдельных слоев, особенности межслоевых интерфейсов. Предложены способы синтеза нанопроволок с тонкими слоями и четкими границами --- разбавление электролита, использование электрода сравнения, контроль протекшего заряда. Методами магнитометрии изучены слоевые нанопроволоки и показано, что магнитные свойства массива слоевых нанопроволок (в частности, направление оси легкого намагничивания в массиве Co/Cu-НП) зависят не только от аспектного отношения магнитного слоя, но и от отношения толщины слоя магнитного металла к толщине немагнитного спейсера (медной прослойки). При изучении двух типов нанопроволок применялся метод ядерный магнитный резонанс (ЯМР). Методом ЯМР (на ядрах 59Co) изучены слоевые структуры Co/Cu: показано, что в нанопроволоках со слоями меньшей толщины (и, соответственно, с большим вкладом интерфейсов) наблюдается большая доля атомов Co, координированных атомами Cu. Высокая доля атомов, координированных медью, позволяет предположить, что примесь меди входит и в кобальтовые слои. Проведено сравнение гомогенных нанопроволок из железа (ЯМР на ядрах 57Fe) с образцами объемного железа. Обнаружен сдвиг линии в сторону высоких частот (на 0.3 MHz), свидетельствующий об увеличении поля примерно на 0.2 T. Значительное уширение линии и уменьшение времени спин-решеточной релаксации может свидетельствовать о значительном разбросе величин локального магнитного поля. Ключевые слова: нанопроволоки, матричный синтез, микроскопия, элементный анализ, магнитные свойства, ЯМР.

Based on PET track etched membranes, arrays of layer nanowires 100 nm in diameter, consisting of alternating Ni/Cu and Co/Cu layers are grown by the matrix synthesis method. Galvanic deposition processes are studied and conditions for fabricating layer nanowires with different thicknesses for magnetic (Ni or Co) and nonmagnetic (Cu) layer components are determined. An electron microscopic study is performed to verify conditions for fabricating layer nanowires and to correct geometrical sizes of alternating layers. Magnetization curves of produced arrays of layer nanowires are measured by vibration magnetometry methods at room temperature for two extreme orientations of a scanning magnetic field, i.e., parallel and perpendicular ones with respect to the nanowire growth axis. It is shown that the magnetic anisotropy of the nanowire array is controlled not only by the chemical composition, but also the thickness and alternation period of magnetic metal layers in nanowires. The dependence of the magnetostatic energy and demagnetizing field in the synthesized layer nanowires on the magnetic metal filling factor is numerically evaluated; the results are in qualitative agreement with experimental observations.

Arrays of layered nanowires (NWs) with a diameter of 100 nm consisting of alternating layers of Ni/Cu and Co/Cu were obtained by matrix synthesis based on polyethylene terephthalate track etched membranes. The process of galvanic deposition was studied and the regimes of obtaining of layered nanowires with different thicknesses of magnetic (Ni or Co) and non-magnetic (Cu) components of layers were determined. Electron microscopic investigation was performed to verify regimes of obtaining of layered nanowires and to refine the geometric properties of alternating layers. Using vibration magnetometer, the magnetization curves of the obtained arrays of layered NWs was measured at room temperature for two limiting orientations of the scanning magnetic field: parallel and perpendicular to the growth axis of the NW. It is shown that the magnetic anisotropy of the NW array is determined not only by the chemical composition, but also by the thickness and period of alternating magnetic layers in the NW. Numerical calculations of the dependence of the magnetostatic energy and the magnitude of the demagnetizing field in the synthesized layered NWs on the factor of their filling with a magnetic metal are carried out, which are qualitatively consistent with experimental observations.

This article discusses the use of scanning microscopy in the study of one-dimensional nanostructures – nanowires. The nanowires were produced by matrix synthesis. Atomic force microscopy (AFM) of conical nanowires was carried out, and layered nanowires were investigated by AFM and magnetic force microscopy (MFM) methods.

AbstractNanowires (NWs) consisting of Ni/Cu and Co/Cu alternating layers with a diameter of 100 nm and layer thicknesses varying between 10 and 500 nm are prepared by template synthesis in pores of polymer track-etched membranes. Bath compositions and different regimes for pulsed electrodeposition of NWs are explored. A procedure for electrodeposition of NWs using pulses of equal charge is developed. By diminishing the amount of charge per pulse, initially we manage to lower the layer thickness to 10–15 nm, but further diminishing of charge in pulses leads to the blending of elemental composition of adjacent layers and/or formation of rod–shell nanostructures within the NWs. The coercive force (15–30 mT) and residual magnetization of our layered NWs are determined from magnetization measurements. For NWs with a layer thickness of 50–100 nm, the magnetization curves recorded in the out-of-plane and in-plane geometries are similar in shape and have similar parameters. For NWs with thicker layers (250 and 500 nm), magnetization curves are markedly different due to magnetic anisotropy (an easy magnetization axis emerges longitudinally to NWs) and interference between neighboring NWs. Magnetic force microscopy of isolated NWs identifies that the NWs comprise magnetic regions extending over ~100–150 nm. The NW can be partially remagnetized by applying an external magnetic field (+16 mT) longitudinally.

AbstractNanowires (NWs) consisting of Ni/Cu and Co/Cu alternating layers with a diameter of 100 nm and layer thicknesses varying between 10 and 500 nm are prepared by template synthesis in pores of polymer track-etched membranes. Bath compositions and different regimes for pulsed electrodeposition of NWs are explored. A procedure for electrodeposition of NWs using pulses of equal charge is developed. By diminishing the amount of charge per pulse, initially we manage to lower the layer thickness to 10–15 nm, but further diminishing of charge in pulses leads to the blending of elemental composition of adjacent layers and/or formation of rod–shell nanostructures within the NWs. The coercive force (15–30 mT) and residual magnetization of our layered NWs are determined from magnetization measurements. For NWs with a layer thickness of 50–100 nm, the magnetization curves recorded in the out-of-plane and in-plane geometries are similar in shape and have similar parameters. For NWs with thicker layers (250 and 500 nm), magnetization curves are markedly different due to magnetic anisotropy (an easy magnetization axis emerges longitudinally to NWs) and interference between neighboring NWs. Magnetic force microscopy of isolated NWs identifies that the NWs comprise magnetic regions extending over ~100–150 nm. The NW can be partially remagnetized by applying an external magnetic field (+16 mT) longitudinally.

Nanowires (NWs) consisting of Ni/Cu and Co/Cu alternating layers with a diameter of 100 nm and layer thicknesses varying between 10 and 500 nm are prepared by template synthesis in pores of polymer track-etched membranes. Bath compositions and different regimes for pulsed electrodeposition of NWs are explored. A procedure for electrodeposition of NWs using pulses of equal charge is developed. By diminishing the amount of charge per pulse, initially we manage to lower the layer thickness to 10–15 nm, but further diminishing of charge in pulses leads to the blending of elemental composition of adjacent layers and/or formation of rod–shell nanostructures within the NWs. The coercive force (15–30 mT) and residual magnetization of our layered NWs are determined from magnetization measurements. For NWs with a layer thickness of 50–100 nm, the magnetization curves recorded in the out-of-plane and in-plane geometries are similar in shape and have similar parameters. For NWs with thicker layers (250 and 500 nm), magnetization curves are markedly different due to magnetic anisotropy (an easy magnetization axis emerges longitudinally to NWs) and interference between neighboring NWs. Magnetic force microscopy of isolated NWs identifies that the NWs comprise magnetic regions extending over ~100–150 nm. The NW can be partially remagnetized by applying an external magnetic field (+16 mT) longitudinally.

Magnetic nanowires (NWs) of pure Fe,Co, Ni, alloys FeCo, FeNi and layered Ni/Cu were obtained by galvanic deposition into the pores of track membranes. The process of deposition was investigated and non-linear character was found. The obtained ensembles of NWs were tested by SEM, TEM, X-ray, Magnetometry and Mässbayer spectroscopy. Element concentration in NWs is differ from concentration of electrolyte and change slightly along the NW length (for alloys). For layer NWs the layers thickness and composition was determined. Different phases in alloys were found. Magnetometry measurements confirmed the magneto-hard properties of FeCo NWs and soft magnetic properties of FeNi NWs. It was also shown that increase of grooving voltage leads to increase of magneto-hard properties due to formation of microcrystalline structure.