An algorithmic approach for determining the relationship between the energy of grain boundaries and their location in the structure has been developed and proposed. A comparative analysis of the results of relative grain boundary energies measurements by the method of etch groove shape analysis for “manual” measurement and the developed algorithmic approach was carried out on the example of ultrafine-grained nickel obtained by severe plastic deformation.

An approach that allows a qualitative and quantitative analysis of the grain structure of ultrafine grained nickel by electrochemical etching surface is proposed. The data on the etching relief of ultra-fine-grained nickel obtained by scanning tunneling microscopy are analyzed. The bimodality of the structure is revealed, which is confirmed by statistical analysis.

The influence of the state of interfaces on the magnetoresistive properties of Co/Cu superlattices has been studied by the methods of nuclear magnetic resonance and X-ray reflectometry. It has been found that the magnetron-sputtered superlattices with the highest value of the giant magnetoresistance effect have the largest fraction of highly perfect Co/Cu interlayer boundaries, as well as practically the smallest fraction of cobalt atoms localized in the interfaces.

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.

Using the template synthesis method, nanowires (NWs) of various types are prepared from pure cobalt, an alloy of cobalt with copper, and layered structures comprised of alternating cobalt layers of various thicknesses and copper interlayers. Using the method of nuclear magnetic resonance (NMR) on 59Co nuclei, structural features of the arrays have been investigated. It is established that fcc and hcp Co phases are present in single-component NWs; the addition of copper ions to the electrolyte leads to almost complete disappearance of the hcp Co phase in the NW. Parameters that characterize the structure of interlayer boundaries of layered NWs with different layer thicknesses are determined.

Effects of Cu layer thicknesses and annealing temperature on structural features of Co/Cu superlattices have been studied by nuclear magnetic resonance (NMR), electron microscopy, X-ray diffraction and X-ray reflectometry. Determination of a fraction of perfect boundaries and of Co atoms in interfaces based on NMR studies is demonstrated. Correlation of these parameters with the probability of a single electron scattering event at an interface and magnetoresistance is analyzed.

The state of interfaces in Co/Cu superlattices with various thicknesses of non-magnetic Cu layers (tcu) has been studied by the methods of nuclear magnetic resonance (NMR) and X-ray reflectometry. The samples glass/Fe(5 nm)/[Co(1.5 nm)/Cu(tcu)]10/Cr(3 nm) were fabricated by the method of magnetron sputtering on glass substrates under constant current in the ULVAC MPS-4000-C6 device. The 59Co NMR spectra were taken in a local magnetic field in the frequency range of 90–240 MHz at 4.2 K in the pulsed NMR spectrometer. The spin echo signal was formed by a sequence of two coherent radio-frequency pulses (τp)x − tdel − (τp)y − tdel – echo forming an alternate magnetic field with the round component amplitude H1 of about 10 Oe in a resonance coil. It has been shown both by NMR and X-ray reflectometry that the structure of interfaces deteriorates with an increase of the Cu layers thickness, and similar dependences of the parameters characterizing structural imperfection of interfaces were obtained by these two methods.

The effect of the structure of interfaces on the magnetoresistance properties of CoFe/Cu superlattices has been studied by the method of nuclear magnetic resonance (NMR).It was found that, with increasing annealing temperature, the number of Co atoms involved in the formation of interlayer boundaries increases and the fraction of highly perfect interfaces decreases.It is demonstrated that the deteriorated state of interlayer boundaries results in a decrease in GMR.

The influence of the interface structure on the magnetoresistive properties of Co/Cu superlattices has been studied using the techniques of nuclear magnetic resonance and X-ray reflectivity. It has been found that the roughness of interfaces and the number of cobalt atoms involved in their formation increase with annealing temperature, while the fraction of highly perfect interfaces decreases at higher temperatures. It has been demonstrated that the probability of the scattering of conduction electrons by interfaces increases with the width of these boundaries.

Structure, magnetic and magnetoresistive properties of spin valves with Ni-Fe-Mn antiferromagnet as a pinning layer have been studied. A technique of fabrication of spin valves with an enhanced thermal stability and improved hysteretic characteristics has been elaborated.

The influence of heat treatment on the phase composition and magnetic properties of singlelayer Ni-Fe-Mn films are investigated.Samples of (Ni 80 Fe 20 ) 60 Mn 40 (50nm)/Ta (5nm) were prepared by direct current magnetron sputtering on glass substrates.It is shown that annealing leads to a phase separation of the fcc solid solution of Ni-Fe-Mn on permalloy and manganese.In annealed samples, when the sample is cooled in a magnetic field, unidirectional anisotropy is formed due to the exchange interaction of the ferromagnetic regions of Ni 80 Fe 20 and the antiferromagnetic regions of Mn.The exchange bias of the magnetic hysteresis loop is H ex = 317 Oe.

Институт физики металлов УрО РАН 620108

Magnetic properties of bilayers based on the Ni-Fe-Mn antiferromagnetic phase are studied, as well as magnetic and magnetoresistive properties of a bottom spin valve (SV) with a Ni-Fe-Mn antiferromagnet as a pinning layer.A technique for the fabrication of bottom spin valves with enhanced thermal stability and improved hysteretic characteristics has been developed.Specimens were made by DC magnetron sputtering and electron-beam evaporation on glass (Corning) and single-crystalline sapphire (1012).For the preparation of bottom SV, the specimens were etched in a PlasmaPro NGP 80 RIE Oxford Instruments reactive ion-plasma etching device.The magnetoresistance of the as-fabricated Al 2 O 3 /Ni-Fe-Mn/Co 90 Fe 10 (5.5 nm)/Cu(3.6nm)/Co 90 Fe 10 (5.5 nm)/Ta(5 nm) spin valve is R/R s = 3.8 %.

Methods of nuclear magnetic resonance and X-ray reflectometry have been used to investigate the state of interfaces in Co/Cu superlattices with different thicknesses of the nonmagnetic layers of Cu. It has been shown that, with an increase in the thicknesses of Cu layers, the perfection of the structure of the interfaces deteriorates.

The method of nuclear magnetic resonance has been used to investigate the structural features of the interfaces in [Co/Cu] n sublattices prepared using the method of magnetron sputtering. Changes in the structural characteristics of the interfaces and magnetoresistive properties of the sublattices have been analyzed depending on the number n of Co/Cu bilayers. Correlations have been found between the magnitude of the magnetoresistance and structural characteristics of the interfaces.