Study of the mechanisms of the solid-state reactions in Sn/Fe/Cu thin films is interesting both from a fundamental point of view and from a view of the importance of emerging intermetallics in the technology of solder joints and thin-film lithium-ion batteries. By the integrated approach, including both X-ray phase analysis and local elemental analysis of the cross-sections of the films, the phase composition and the mutual arrangement of phases were studied, at various stages of the solid-state reaction occurring at different temperatures. The observed sequence of the appearing phases differs significantly from the expected one if the mass transfer took place by a volume diffusion through the forming layers.

The study of the formation of the Cu6Sn5 intermetallic compound in Sn(55nm)/Cu(30nm) thin bilayer films was carried out directly in the column of a transmission electron microscope (electron diffraction mode) by heating the film sample from room temperature to 300 °C and recording the electron diffraction patterns. The thin films formed as a result of a solid state reaction were monophase and consisted of the η-Cu6Sn5 hexagonal phase. The temperature range for the formation of the η-Cu6Sn5 phase was determined. The estimate of the effective interdiffusion coefficient of the reaction suggests that the main mechanism for the formation of the Cu6Sn5 intermetallic is diffusion along the grain boundaries and dislocations.

AbstractThe structural and magnetic properties of granular Co–In_2O_3 nanocomposite films formed by vacuum annealing of In/Co_3O_4 film bilayers at a temperature of 550°C have been investigated. The synthesized Co–In_2O_3 films contain ferromagnetic cobalt nanoclusters with an average size of 60 nm and a magnetization of ~340 emu/cm^3 surrounded by the In_2O_3 layer and exhibit the thermally activated conductivity.

AbstractIt is shown that annealing 550°C of the Fe/Pt bilayer films fabricated by layer-by-layer deposition onto polycrystalline Al_2O_3 substrates in an atomic ratio of Fe: Pt = 71: 29 leads to the formation of the inplane rotational magnetic anisotropy with the easy axis that can be aligned by magnetic field in any direction in the film plane. The increase in the Pt content in the investigated film system to 50 at % leads to an increase in the anisotropy constant to 6.5 × 10^6 erg/cm^3, which exceeds the value in the Fe_71Pt_29 sample by a factor of 6. In addition to the rotational anisotropy, the Fe50Pt50 films are characterized by the perpendicular rotational magnetic anisotropy, which is higher than the film shape anisotropy. Therefore, the easy axis in these samples can be aligned by magnetic field in any spatial direction. According to the X-ray and magnetic measurement data, the synthesized samples have a polycrystalline structure consisting of two ordered phases: magnetically hard L1_0–FePt and magnetically soft L1_2–Fe_3Pt. This gives us grounds to suggest that the rotational magnetic anisotropy originates from the epitaxial intergrowth and exchange coupling of these two phases.

AbstractThe results of structural and magnetic investigations of nanogranular Co–Al_2O_3 films formed from Co_3O_4/Al thin-film layered structures upon vacuum annealing are reported. The Co_3O_4/Al films have been obtained by sequential reactive magnetron sputtering of a metallic cobalt target in a medium consisting of the Ar + O_2 gas mixture and magnetron sputtering of an aluminum target in the pure argon atmosphere. It is shown that such a technique makes it possible to obtain nanogranular Co–Al_2O_3 single- and multilayer thin films with a well-controlled size of magnetic grains and their distribution over the film thickness.

Представлены результаты исследования структурных и магнитных свойств пленок Fe87Pt13, синтезированных с использованием твердофазных реакций, и композитных пленок Fe87Pt13-Al2O3, полученных с помощью метода алюмотермии. Показано, что в синтезированных образцах обоих типов присутствует вращающаяся магнитная анизотропия, заключающаяся в том, что направление легкой оси намагничивания в плоскости пленки может устанавливаться магнитным полем. Установлено, что в композитных Fe87Pt13-Al2O3 пленках величина вращающейся магнитной анизотропии на порядок выше, чем в образцах Fe87Pt13. Сделано предположение, что природа вращающейся магнитной анизотропии связана с обменным взаимодействием L10-FePt фазы с L12-Fe3Pt фазой в пленках Fe87Pt13 и с магнитными окислами железа в образцах Fe87Pt13-Al2O3. Исследование выполнено при финансовой поддержке РФФИ в рамках научных проектов N 16-03-00069 и 15-02-00948, и частично правительства Красноярского края, КФН, РФФИ (проект N 16-42-243006). DOI: 10.21883/FTT.2017.02.44066.262

The original Co(001)/Pt(111) film structures are obtained by consequent thermal deposition layer with a cubic crystal lattice and Pt(111) from the target, sprayed using a magnetron sputtering technique on a single crystal substrate of MgO(001) in a vacuum of 10 -6 Torr. In the experiments,samples1Сo:3Pt and1Сo:1Pt atomicratio of the totalthickness of about 300 nm are used.Initial samples were annealed inthe temperature range fromto250 oCto850 oCinincrements of 50 for 40 minutes. X-ray diffraction analysis showed that in two-layer structures with the atomic ratio of reagents 1/3, at temperatures of annealing at T = 500 and 850 oС in the interlayer chemical interaction to form phase epitaxial cubic compounds CoPt 3 (L1 2 ) c FCC-lattice (a = 3.856 A). Annealingof thesesamestructures with 1/1lead to the formation of the second phaseCoPt(L1 0 )withtetragonal distortion, which helps to ensure ahigh value ofthe uniaxialmagnetocrystallineanisotropyconstantK 1 anddetermineseasymagnetization direction(axisc).Synthesizedsample consisting oftwomagnetic phases isthe saturation magnetization, comparable with the value ofM S for the filmL1 2 -CoPt 3 ,planaranisotropywithK 1 = 5.6 ·10 5 erg / sm3andH c ~10 3 E.Newly formedL1 0 -CoPtphasegrowsepitaxiallyon the basis ofpre-synthesized L1 2 -CoPt 3 phasewith the sameorientation relationship. The newly formedL1 0 -CoPtphasegrowsepitaxiallyon the basis ofpre-synthesized L1 2 -CoPt 3 phasewith the sameorientation relationship. Featuresfilms withatomic ratio of Co / Pt = 1/1 at T = 850 oCis the presence of“rotational” anisotropy due to the exchange interactionof twoordered phases formedCoPt (111) and CoPt 3 (111) with a ferromagneticorder andan easy axis, which can beapplied a magneticfieldto refocus. By changing the ratio of the reactantsin the system, it is possible tochange the sequence ofphase formation.

Taking for example the initiation of the classical solid-state reaction between Fe2O3 and Al layers in films, it was shown that as a result, the granular Fe–Al2O3 films consisting of Fe nanoclusters embedded in an insulating Al2O3 matrix were made. It follows from the reaction equation that the Fe volume fraction in granular films is less than the percolation limit. This fact defines the magnetic properties of iron clusters, which are superparamagnetic. It is supposed that a nanocrystalline microstructure must be present in thin films after solid-state reaction, which occurs in self-propagating high temperature synthesis conditions.

Solid-phase reactions taking place in Al/β-Co/MgO(001) and Al/α-Co/MgO(001) film systems under conditions of self-propagating high-temperature synthesis (SHS) are investigated. In both systems, SHS products exhibit the single CoAl superstructure, which epitaxially grows on the MgO(001) surface in the Al/β-Co/MgO(001) structures and has a fine-dispersed disordered structure in the Al/α-Co/MgO(001) films. It appears that the difference in the reagent structure has an effect on the energy of activation but does not change the SHS initiation temperature and the temperature at which the initial phase involved in the reaction products nucleates. It is shown that the SHS initiation temperature in the Al/β-Co/MgO(001) and Al/α-Co/MgO(001) systems coincides with the temperature of CoAl superstructure ordering.