Unconventional critical behavior near the phase transition temperature and magnetocaloric effect in La0.5Ca0.4Ag0.1MnO3 compound
The critical behavior associated with the magnetic phase transition has been investigated by magnetization isotherms in La0.5Ca0.4Ag0.1MnO3(LCAMO) powder. The X-ray diffraction characterization has revealed that this sample crystallized in the orthorhombic symmetry with Pnma space group. While the experimental results revealed that this sample underwent a paramagnetic-ferromagnetic transition, the magnetic measurements data indicated that the compound exhibited a second-order phase transition. Furthermore, the critical exponents values were found as β = 0.79, γ = 0.71 and δ = 1.828 with TC= 189.87 K. The relative cooling power of the sample was determined as 14.70 J/kg under a magnetic field of 1 T making it a potential working material in magnetic refrigeration.
Experience in the Development of a Configurable Laboratory UV Projection Photolithography System of Micron Resolution
The possibility of creating a laboratory UV photolithography setup with the help of commercially available components, such as optical-mechanical positioners and UV (ultraviolet) objective lenses, is discussed. Existing technical solutions concerning the optical systems of optical lithography, which rely on object‒image reduction, are considered. The main trends in the design of such systems based on lens optics are analyzed. The theoretical and practical aspects underlying the design of similar systems are examined taking into account the basic conditions of image obtainment: congruence to the initial object, ray-path telecentricity, and achievement of the required parameters by linear fields and resolution.
Polycrystalline magnetite (Fe3O4) thin films from FeOx/Fe bilayers grown by pulsed laser depositions
The effect of heat treatment on the structural and magnetic properties of bilayered FeOx/Fe thin films grown by pulsed laser deposition on pre-oxidized amorphous SiO2/Si substrates has been studied. Post-deposition vacuum thermal annealing leads to remarkable changes in the structural and magnetic properties of the FeOx layer, which has been investigated by the combination of scanning electron and atomic force microscopy, Raman scattering spectroscopy and conversion electron Mössbauer spectroscopy. FeOx layer deposited at room temperature on top of the polycrystalline Fe underlayer is amorphous with the smooth surface (root mean square roughness ~ 0.5 nm). Vacuum thermal annealing of the FeOx/Fe stack at T = 500 °C leads to the formation of a polycrystalline Fe3O4/Fe thin film structurewith the magnetite nucleation centers of an average size of 100 nm. The formation of the exact magnetite phase depends on the annealing conditions as shown by in-situ Raman and Mössbauer spectroscopy investigations.
Periodical multilayer (ML) structures can be used as generators of X-ray standing waves (XSW) for investigation of objects and processes on solid/liquid and solid/gas interfaces. In this paper, we investigate the specific requirements to the structural properties of the multilayer structures for XSW application. We consider the effect of typical defects in the ML structure on the X-ray standing wave formation and show that the X-ray standing wave is very robust against the random imperfection in the multilayer structure. In contrast, the roughness of the topmost layer will have a strong influence on the XSW experimental results, as the ML serves as a support for the investigated objects, so that the surface geometry gets directly translated into the objects. In the experimental part of this work, we have used the ion-beam deposition to grow Ni/Al metal- and metal oxide-based multilayers and investigate with AFM their surface quality. The presented results demonstrate that metal oxides can be successfully used as basic material for X-ray multilayer standing wave generators.
We report here the growth and functional properties of silicon-based nanowhisker (NW) diodes produced by the vapor–liquid–solid process using a pulsed laser deposition technique. For the first time, we demonstrate that this method could be employed to control the size and shape of silicon NWs by using a two-component catalyst material (Au/Cu ≈ 60:1). During the NW growth, copper is distributed on the outer surface of the NW, whereas gold sticks as a droplet to its top. The length of NWs is defined by the total amount of copper in the catalyst alloy droplet. The measurements of the electrical transport properties revealed that in contact with the substrate, individual NWs demonstrate typical I–V diode characteristics. Our approach can become an important new tool in the design of novel electronic components.
La1−xSrxMn0.5Сo0.5O3 (x ≤ 0.75) perovskites have been studied as a function of temperature by neutron powder diffraction (NPD), magnetization and magnetoresistance measurements. The NPD data show that x = 0.15 and 0.5 compounds are stoichiometric, so the Sr2+ doping transforms Co2+ ions into the Co3+ ones, whereas manganese ions remain in the 4+ oxidation state as in the parent ferromagnetic compound . The magnetization data show a decrease in the Curie temperature from 215 K for the compound with x = 0 down to 147 K for the compound with x = 0.05. The compounds with x > 0.15 show an increase in TC up to 260 K (x = 0.75) in spite of a gradual decrease of the spontaneous magnetization. The stoichiometric compound x = 0.5 demonstrates a sharp ferromagnet-paramagnet transition with TC = 250 K. However, there is no visible coherent magnetic contribution to the NPD patterns. All compounds are semiconductors and exhibit large magnetoresistance gradually increasing with decrease of temperature. The magnetic data have been interpreted assuming that the Co3+ ions are in high spin state, however, there is a fraction of cobalt ions in low spin state. It is suggested that the superexchange interaction between Co3+ ions in the high spin state and Mn4+ ions is ferromagnetic and that the ferromagnetism of the compounds with x > 0.5 and high TC is associated with positive exchange interactions between Co3+ being in high spin state and Mn4+ ions distributed within the short range regions. Based on the NPD results and magnetization data the magnetic phase diagram has been constructed.
Solid-state ionization chambers are presented based on thin diamond crystals that allow pulse-resolved intensity measurements at a hard X-ray free-electron laser (FEL), up to the 4.5 MHz repetition rate that will become available at the European XFEL. Due to the small X-ray absorption of diamond the thin detectors are semi-transparent which eases their use as non-invasive monitoring devices in the beam. FELs are characterized by strong pulse-to-pulse intensity fluctuations due to the self-amplified spontaneous emission (SASE) process and in many experiments it is mandatory to monitor the intensity of each individual pulse. Two diamond detectors with different electrode materials, beryllium and graphite, were tested as intensity monitors at the XCS endstation of the Linac Coherent Light Source (LCLS) using the pink SASE beam at 9 keV. The performance is compared with LCLS standard monitors that detect X-rays backscattered from thin SiN foils placed in the beam. The graphite detector can also be used as a beam position monitor although with rather coarse resolution.
Funding for this research was provided by:
Office of Science (DE-AC02-76SF00515)
Magnetic and magnetotransport properties of La0.7Sr0.3Mn1−xCoxO3 ceramics have been investigated by neutron powder diffraction, magnetization and electrical measurements. It is shown that substitution by cobalt ions leads to a decrease of magnetic transition temperature down to 140 K for the compound with x = 0.33. The compounds with cobalt content 0.4 < x < 0.6 are characterized by a presence of small ferromagnetic component due to exchange interactions between cobalt and manganese ions with maximal transition temperature of about 190 K observed for x = 0.5. Further increase of the dopant concentration diminishes ferromagnetic interactions. An evolution of electronic configuration of manganese and cobalt ions upon chemical substitution as well as related changes in the exchange interactions which determine the type of the magnetic state are discussed. Based on the neutron diffraction results and magnetometry data the preliminary magnetic phase diagram has been constructed.
Analysis of anomalous negative magnetic contribution to thermal expansion in Sm0.80B6and pseudobinary compounds Sm1-xLaxB6(x = 0, 0.10, 0.22, 0.50)
This study is the first attempt to apply the two-level Weiss model for the invar alloy to intermediate-valence samarium systems. This model is instrumental in giving a quantitative characterisation of the anomalous magnetic contribution to the coefficient of thermal expansion (CTE) of Sm0.80B6 and Sm1−xLaxB6 (x = 0, 0.10, 0.22, 0.50). A good agreement between the experimental and calculated magnetic contributions to the CTE is achieved for Sm0.78La0.22B6 over the temperature range from 0 K to 210 K. In other systems, a good fit is obtained over shorter temperature ranges. The model parameters and the dependence of the CTE minimum on the level of lanthanum doping in SmB6 are presented.
In this paper lattice dynamics of dodecaborides RB12 (R = Zr, Yb, Lu) is studied using the superatom model. Within this model, a group of strongly bound boron atoms placed at the vertices of cubooctahedron is substituted with a superatom, which possesses the mass equal to the sum of the masses of all atoms in the cluster. Based on this approach, phenomenological models for Yb(Lu)B12 and ZrB12 describing phonon dispersion up to 45 meV for Yb(Lu)B12 and up to 35 meV for ZrB12 are developed. Good agreement between experimental and modeled dispersion curves is found in both acoustic and low-energy optic regions for ZrB12, while in Yb(Lu)B12, description of acoustic phonons can only be regarded as satisfactory. The comparison with Einstein oscillator approximation is presented. Analysis of the interatomic interactions is performed on the basis of the Born von Karman force constants model. It is shown that the model makes it possible to calculate specific heat with a 5% error margin up to approximately 100 K, while a more commonly used Debye model only provides correct values up to 60 K.
Anomalous behavior of displacement correlation function and strain in lanthanum cobalt oxide analyzed both from X-ray powder diffraction and EXAFS data
A combined X-ray powder diffraction (XPD) and high-resolution extended X-ray absorption fine structure (EXAFS) at the Co and Ga K-edges study has been performed for LaCoO3 and LaGaO3 ceramics, the latter sample was used as a reference without spin transitions. Based on the X-ray diffraction data, we have found that isotropic atomic displacement parameters (ADP) or mean-squared displacement of the Co–O bond exhibit gradual growth below ~50 K, wherein the strain dependencies testify rapid increase below 150 K for the LaCoO3 having rhombohedral structure. No similar features could be observed for LaGaO3 sample. Above ~100 K the isotropic ADP of the Co–O bond indicate a gradual growth, whereas strain curves show distinct bend near the spin-state transition temperature at about 150 K. According to the EXAFS data, the correlated parallel mean squared relative displacement (MSRD||) of Co–O and Ga–O bonds exhibit a gradual growth above 150 K; however, in the LaCoO3 this parameter is notably bigger. It is supposed that at low temperature the cobalt ions are dominantly in low-spin (LS) state, while certain amount of Co3+ ions located within the surface layer of the crystallines have high-spin state (HS). Temperature growth leads to a gradual transformation of the HS state of the cobalt ions into the highly-hybridized intermediate-spin (IS) state, while the cobalt ions located in the inner part of the crystallines remain LS configuration up to 150 K. Further temperature increase leads to a spin transition of the Co3+ ions located within the crystallines from the LS state into the IS one.
A combination of neutron diffraction, synchrotron X-ray diffraction, and high-resolution extended X-ray absorption fine structure measurements has been used to clarify the correlations between long- and local-range structural distortions across the spin-state transition in powders of LaCoO3 and La0.5Sr0.5Co0.75Nb0.25O3. The analysis of the diffraction data has revealed that the isotropic thermal parameters of Co–O bond abnormally increase below 100 K in both samples, while the temperature dependence of the average Co–O bond lengths is linear from 10 to 300 K. We also have found that the Co–O bond lengths are larger in La0.5Sr0.5Co0.75Nb0.25O3, as compared with the ones in LaCoO3. The X-ray absorption data showed an anomalous decrease of the Co–O bond lengths only for LaCoO3, in contrast to the bond length values obtained by diffraction. The structural anomalies observed by spectroscopy measurements are discussed in terms of the spin-state transition model.
Ceramics samples of La1–xSrxMn0.5Ni0.5O3 (0 ≤ x ≤ 0.2) with perovskite structure have been studied by neutron diffraction method, magnetometry and magnetoresistance measurements. Structural data testify a partial order of the Ni and Mn ions in all the compounds in spite of chemical substitution of the La3+ions by Sr2+ ones and an increase of the oxidation state of the Ni ions from 2+ towards to 3+ one. Magnetic structure of the compounds changes from ferromagnetic one (specific for the compound with x = 0) to antiferromagnetic (compounds with x ≥ 0.1) while the temperature of a transition into paramagnetic state remains about 270 K for all the samples. Magnetoresistance gradually decreases with temperature increase and strontium content. The results are discussed assuming nearly equal ferromagnetic and antiferromagnetic components of the superexchange interaction Ni2+–O–Mn4+while the interaction between Ni3+ and Mn4 ions is considered to be strongly antiferromagnetic.
Troyanchuk, I. O., et al. "Antiferromagnet-ferromagnet transition in La1–xSrxMn0. 5Ni0. 5O3 (0≤ x≤ 0.2) ceramics." Low Temperature Physics 43.8 (2017): 982-985.
© 2017 International Union of Crystallography. Beryllium, being one of the most transparent materials to X-ray radiation, has become the material of choice for X-ray optics instrumentation at synchrotron radiation sources and free-electron laser facilities. However, there are concerns due to its high toxicity and, consequently, there is a need for special safety regulations. The authors propose to apply protective coatings in order to seal off beryllium from the ambient atmosphere, thus preventing degradation processes providing additional protection for users and prolonging the service time of the optical elements. This paper presents durability test results for Be windows coated with atomic-layer-deposition alumina layers run at the European Synchrotron Radiation Facility. Expositions were performed under monochromatic, pink and white beams, establishing conditions that the samples could tolerate without radiation damage. X-ray treatment was implemented in various environments, i.e. vacuum, helium, nitrogen, argon an d dry air at different pressures. Post-process analysis revealed their efficiency for monochromatic and pink beams.Beryllium, being one of the most transparent materials to X-ray radiation, has become the material of choice for X-ray optics instrumentation at synchrotron radiation sources and free-electron laser facilities. However, there are concerns due to its high toxicity and, consequently, there is a need for special safety regulations. Here, durability test results for Be windows coated with atomic-layer-deposition alumina layers run at the European Synchrotron Radiation Facility are presented.
Yurkevich, Oksana, et al. "Protective radiolucent aluminium oxide coatings for beryllium X-ray optics." Journal of synchrotron radiation 24.4 (2017).
The formation of thin films of the different stable and metastable titanium oxide phases is demonstrated by cathode arc sputtering of a titanium target in an oxygen atmosphere. We also show that sputtering of titanium in vacuum yields the formation of titanium silicides on the silicon substrate. The crystal structure of the produced samples was investigated using Raman spectroscopy and X-ray diffraction. We conclude that cathode arc sputtering is a flexible method suitable for producing the functional films for electronic applications. The functionality is verified by the memory effect demonstration, based on the resistive switching in the titanium oxide thin film structure.
Shvets, Petr, et al. "Cathodic arc sputtering of functional titanium oxide thin films, demonstrating resistive switching." Physica B: Condensed Matter 513 (2017): 15-20.
Neutron powder diffraction (NPD) and magnetization measurements have been performed for the La0.7Sr0.3Mn0.7Ti0.3−xAlxO3 (0≤x≤0.15) stoichiometric compounds. Increase of the Al3+content enlarges the fraction of Mn4+ ions from 0% for the sample with x=0 up to around 20% for x=0.15 one. The compound without Al content undergoes a structural transition from rhombohedral phase to orbitally disordered orthorhombic one below room temperature whereas crystal structure of the compounds with x=0.1 and 0.15 remain to have rhombohedral one down to 2 K. The structural transition occurs well above the magnetic transition temperature. The substitution of Ti4+ by Al3+ ions is accompanied by a gradual increase in the bond angle Mn–O–Mn and Mn–O bond length thus strengthening the covalent component of the related chemical bonds. All these compounds are insulators and have ferromagnetic components. Magnetic moments calculated per manganese ion based on NPD data obtained at 2 K are found to change from 1.3 µB for x=0 compound up to 1.7 µB for x=0.1 and 0.15 ones. It is suggested that ferromagnetism is predominantly caused by superexchange interactions Mn3+–O–Mn3+ and Mn3+–O–Mn4+ whereas fluctuations in the bond angles and distances frustrate magnetic interactions. It is assumed that increase of covalency within the chemical bonds Mn–O slightly enforces ferromagnetic interactions.
Troyanchuk, I. O., et al. "Magnetic ordering in manganites doped by Ti and Al." Ceramics International 43.1 (2017): 187-191.
Book Chapter "Smart Materials for Smart Living"
Ceramic samples of La1-xSrxMn0.5Ni(Co)0.5O3 with perovskite structure are considered to be promising functional materials due to their intriguing magnetic and magnetoresistive properties. Physical properties of these compounds dependent on their structural parameters and electron configuration of the related transition metal ions. These compounds have been thoroughly studied by neutron diffraction technique, magnetometry and magnetoresistance measurements. The obtained results have allowed us to determine the evolution of the structural parameters of the compounds upon chemical substitution while their crystal structure remains to be rhombohedral up to the dopant concentration of 20%, in the case of the Co-doped compounds further increase of Sr content favors a stabilization of cubic structure. The substitution by strontium ions leads to a degradation of long-range ferromagnetic order attributed to both initial compounds towards either antiferromagnet and spin glass state in the case of Ni and Co containing samples respectively. All the compounds are semiconductors and exhibit large magnetoresistance which gradually increases with temperature decreasing, an increase of strontium concentration leads to a decrease of magnetoresistance effect. The obtained results testify that the chemical substitution leads to an increase in the average oxidationstate of Ni and Co ions from 2+ into 3+ one while manganese ions remain 4+ oxidation state. The character and stability of the superexchange interaction between pairs of Co, Mn and Ni ions via oxygen ion which govern magnetic properties of the compounds are discussed depending on the oxidation state and electron configuration of the respective transition metal ions and structural peculiarities of the compounds. © 2017 Nova Science Publishers, Inc.
In this work, the magnetic and transport properties of Fe/SiO2/Ni and Fe/SiO2/Co multilayers grown on Si/SiO2 substrates have been studied. The samples have been prepared by two-stage deposition process. In the first stage, Fe layer and SiO2 interlayer of both samples are grown by ion beam deposition technique at room temperature. Then the samples are taken out to ambient atmosphere and loaded into a pulse laser deposition (PLD) chamber. Prior to the deposition of top layer, the samples are cleaned by annealing at 150 °C. In the second stage, Ni (or Co) layer is prepared by PLD technique at room temperature. The thickness of deposited layers has been measured by Rutherford back scattering (RBS). Magnetic properties of ferromagnetic bilayers have been investigated by room-temperature ferromagnetic resonance (FMR) and vibrating sample magnetometer (VSM) techniques. Standard four-point magneto-transport measurements at various temperatures have been performed. Two-step switching in the in-plane hysteresis loops of Fe/SiO2/Ni and Fe/SiO2/Co samples is observed. A crossing in the middle of hysteresis loops of both samples points to a weak antiferromagnetic interaction between the magnetic layers of the stacks. Saturation magnetization values have been obtained from the VSM measurements of samples with DC magnetic field perpendicular to the films surface. Magneto-transport measurements have shown the predominant contribution of anisotropic magnetic resistance both at room and low temperatures. FMR studies of Fe/SiO2/Ni and Fe/SiO2/Co samples have revealed additional non-uniform (surface and bulk SWR) modes, which behavior has been explained in the framework of the surface inhomogeneity model. An origin of the antiferromagnetic interaction has been discussed.
Ay, F., Rameev, B.Z., Basaran, A.C. et al. Appl Magn Reson (2017) 48: 85. https://doi.org/10.1007/s00723-016-0849-6
Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu2(SixGe1-x)2
In mixed-valence or heavy-fermion systems, the hybridization between local f orbitals and conduction band states can cause the suppression of long-range magnetic order, which competes with strong spin fluctuations. Ce- and Yb-based systems have been found to exhibit fascinating physical properties (heavy-fermion superconductivity, non-Fermi-liquid states, etc.) when tuned to the vicinity of magnetic quantum critical points by use of various external control parameters (temperature, magnetic field, chemical composition). Recently, similar effects (mixed-valence, Kondo fluctuations, heavy Fermi liquid) have been reported to exist in some Eu-based compounds. Unlike Ce (Yb), Eu has a multiple electron (hole) occupancy of its 4f shell, and the magnetic Eu2+ state (4f7) has no orbital component in the usual LS coupling scheme, which can lead to a quite different and interesting physics. In the EuCu2(SixGe1−x)2 series, where the valence can be tuned by varying the Si/Ge ratio, it has been reported that a significant valence fluctuation can exist even in the magnetic order regime. This paper presents a detailed study of the latter material using different microscopic probes (XANES, Mössbauer spectroscopy, elastic and inelastic neutron scattering), in which the composition dependence of the magnetic order and dynamics across the series is traced back to the change in the Eu valence state. In particular, the results support the persistence of valence fluctuations into the antiferromagnetic state over a sizable composition range below the critical Si concentration xc≈0.65. The sequence of magnetic ground states in the series is shown to reflect the evolution of the magnetic spectral response.
Nemkovski, Krill S., et al. "Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu 2 (Si x Ge 1− x) 2." Physical Review B 94.19 (2016): 195101.
We have investigated the lattice dynamics for a number of rare-earth hexaborides based on the superatom model within which the boron octahedron is substituted by one superatom with a mass equal to the mass of six boron atoms. Phenomenological models have been constructed for the acoustic and lowenergy optical phonon modes in RB6 (R = La, Gd, Tb, Dy) compounds. Using DyB6 as an example, we have studied the anomalous softening of longitudinal acoustic phonons in several crystallographic directions, an effect that is also typical of GdB6 and TbB6. The softening of the acoustic branches is shown to be achieved through the introduction of negative interatomic force constants between rare-earth ions. We discuss the structural instability of hexaborides based on 4f elements, the role of valence instability in the lattice dynamics, and the influence of the number of f electrons on the degree of softening of phonon modes.
Original Russian Text © D.A. Serebrennikov, E.S. Clementyev, P.A. Alekseev, 2016, published in Zhurnal Eksperimental’noi i Teoreticheskoi Fiziki, 2016, Vol. 150, No. 3, pp. 526–535.
Serebrennikov, D.A., Clementyev, E.S. & Alekseev, P.A. J. Exp. Theor. Phys. (2016) 123: 452. https://doi.org/10.1134/S1063776116070220
A quantitative analysis of the crucial characteristics of currently used and promising materials for X-ray refractive optics is performed in the extended energy range 8-100 keV. According to the examined parameters, beryllium is the material of choice for X-ray compound refractive lenses (CRLs) in the energy range 8-25 keV. At higher energies the use of CRLs made of diamond and the cubic phase of boron nitride (c-BN) is beneficial. It was demonstrated that the presence of the elements of the fourth (or higher) period has a fatal effect on the functional X-ray properties even if low-Z elements dominate in the compound, like in YB66. Macroscopic properties are discussed: much higher melting points and thermal conductivities of C and c-BN enable them to be used at the new generation of synchrotron radiation sources and X-ray free-electron lasers. The role of crystal and internal structure is discussed: materials with high density are preferable for refractive applications while less dense phases are suitable for X-ray windows. Single-crystal or amorphous glass-like materials based on Li, Be, B or C that are free of diffuse scattering from grain boundaries, voids and inclusions are the best candidates for applications of highly coherent X-ray beams.
Serebrennikov, Dmitry, et al. "Optical performance of materials for X-ray refractive optics in the energy range 8–100 keV." Journal of synchrotron radiation 23.6 (2016): 1315-1322.
The mesoporous nanographite (NG) film material consisting of tiny flake-like graphite crystallites of nanometer-scale thickness is deposited onto carbon fibers with diameter of few micrometers using adapted plasma enhanced chemical vapor deposition (CVD) method. Macroscopic morphology parameters of NG material depend on deposition time duration so, that thickness of the NG coating is increased from 0.5 to 2 μm, whereas the average sizes of the individual crystallites and the pores between them are decreased from 0.5 to 0.1 nm, with deposition time extension from 15 to 60 min, respectively. The high resolution electron microscopy examinations indicate that the NG flakes consist of parallel graphene layers separated by about 0.34 nm and those layers are paired at the edges of the flakes producing arced structures. The electrochemical capacitance measurements were served for characterization of the mesoporous nanographite coating; the specific capacitance arising from the electrostatic charge accumulated at the electrode-electrolyte interface was estimated using cyclic voltammetry, galvanostatic charge/discharge measurements, and electrical impedance spectroscopy. The effects of the deposition time duration and other parameters of CVD process on electrochemical performance and structural properties of the prepared NG films are to be discussed.
Magdesieva, Tatiana V., et al. "Electrochemical characterization of mesoporous nanographite films." Carbon 105 (2016): 96-102.
Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties
Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y3Fe5O12 (YIG) on (111)–oriented Gadolinium Gallium Garnetsubstrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the  direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.
Funding for this research was provided by:
Russian Science Foundation (15-12-10038)
Photon Factory, KEK (2014G726)
Program P220 of The Russian Federation Government (14.B25.31.0025)
Sokolov, N. S., et al. "Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties." Journal of Applied Physics 119.2 (2016): 023903.
Thin graphite films attract significant interest due to their unique physical properties and potential applications. Chemical vapor deposition in the presence of metal catalysts is one of the most promising and widely used techniques to produce these films. There are many experimental works devoted to the material synthesis; however, the results are usually obtained by the trial-and-error method without a proper understanding of the processes behind the experiment. We theoretically analyze the carbon diffusion processes inside a metal substrate during the deposition. The theory allows interconnection of the deposition parameters with the thickness of produced graphite films. Numerically solving the diffusion equations for the real systems, we obtained a good correlation between simulations and experimental data. Based on our simulations, we made some conclusions about the formation of graphite films by the precipitation process. The numerical simulations were mostly done for the popular nickel substrates, but we also made some calculations for iron, showing that it also could be used to form thin graphite films under certain conditions.
© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Petr V. Shvets, Alexander N. Obraztsov, "Thin graphite films formation by carbon precipitation in metals: diffusion approach," Journal of Nanophotonics 10(1), 012506 (5 November 2015).https://doi.org/10.1117/1.JNP.10.012506
Effect of annealing on structural and optical properties of Cu2ZnSnS4 thin films grown by pulsed laser deposition
In this work, we compare the effect of different types of thermal annealing on the morphological, structural and optical properties of Cu2ZnSnS4(CZTS) thin films grown by reactive Pulsed Laser Deposition in H2S flow. Rutherford backscattering spectrometry, atomic force microscopy, X-ray diffraction, Raman spectroscopy and optical spectrophotometry data reveal dramatic increase of the band gap and the crystallite size without the formation of secondary phases upon annealing in N2at the optimized conditions.
Surgina, G. D., et al. "Effect of annealing on structural and optical properties of Cu2ZnSnS4 thin films grown by pulsed laser deposition." Thin Solid Films 594 (2015): 74-79.
The results of studying a silicon-germanium (Si-Ge) nanoheterostructure using refractive X-ray optics are described. The diffraction patterns near the silicon Bragg-diffraction peak 400 in the focal plane of refractive lenses are recorded and analyzed. The experiments are carried out in two different geometries: using 1D and 2D X-ray compound refractive lenses.
Original Russian Text © P.A. Ershov, S.M. Kuznetsov, I.I. Snigireva, V.A. Yunkin, A.Yu. Goikhman, A.A. Snigirev, 2015, published in Poverkhnost’. Rentgenovskie, Sinkhrotronnye i Neitronnye Issledovaniya, 2015, No. 6, pp. 55–59.
Ershov, P.A., Kuznetsov, S.M., Snigireva, I.I. et al. J. Synch. Investig. (2015) 9: 576. https://doi.org/10.1134/S1027451015030234
Polycrystalline Ni52Mn36In12 Heusler alloy thin films are synthesized and their magnetic properties, surface morphology, and structure are investigated as a factor of the film thickness and synthesis and vacuum annealing conditions.
Original Russian Text © A.I. Grunin, A.Yu. Goikhman, V.V. Rodionova, S.S. Medvedeva, 2015, published in Poverkhnost’. Rentgenovskie, Sinkhrotronnye i Neitronnye Issledovaniya, 2015, No. 5, pp. 31–36.
Grunin, A.I., Goikhman, A.Y., Rodionova, V.V. et al. J. Synch. Investig. (2015) 9: 451. https://doi.org/10.1134/S1027451015030064
A possible metrological approach to investigation of the optical properties, material structure and profile shape of compound refractive lenses (CRL) is proposed. The methods of X-ray radiography and electron microscopy are proposed for characterization of the profile of a refractive lens with a small curvature radius. Investigation of the material for problems of X-ray optics is performed using small-angle scattering and X-ray microscopy.
Original Russian Text © I.I. Lyatun, A.Yu. Goikhman, P.A. Ershov, I.I. Snigireva, A.A. Snigirev, 2015, published in Poverkhnost’. Rentgenovskie, Sinkhrotronnye i Neitronnye Issledovaniya, 2015, No. 5, pp. 26–30.
Lyatun, I.I., Goikhman, A.Y., Ershov, P.A. et al. J. Synch. Investig. (2015) 9: 446. https://doi.org/10.1134/S1027451015030076
This paper reports a special device called a `speckle suppressor', which contains a highly porous nanoberyllium plate squeezed between two beryllium windows. The insertion of the speckle suppressor in an X-ray beam allows manipulation of the spatial coherence length, thus changing the effective source size and removing the undesirable speckle structure in X-ray imaging experiments almost without beam attenuation. The absorption of the nanoberyllium plate is below 1% for 1 mm thickness at 12 keV. The speckle suppressor was tested on the ID06 ESRF beamline with X-rays in the energy range from 9 to 15 keV. It was applied for the transformation of the phase-amplitude contrast to the pure amplitude contrast in full-field microscopy.
Direct-beam neutron spectra from experimental channels of the IN-06 pulse source at the Institute of Nuclear Research, Russian Academy of Sciences
At the Institute of Nuclear Research, Russian Academy of Sciences, a pulse neutron source IN-06 (spallation source) is commissioned. The direct-beam neutron spectra from experimental channels of the pulse source intended for use in studying condensed media, nanosystems and functional materials are recorded. A comparison of the simulated and experimental neutron spectra shows good agreement. Data for the density of neutron beams at the given functional parameters of the linear proton accelerator, which is the driver of the IN-06 neutron source, are presented.
Original Russian Text © A.A. Alexeev, R.A. Sadykov, V.S. Litvin, E.S. Clementiev, S.N. Axenov, D.N. Trunov, N.M. Sobolevsky, S.F. Sidorkin, E.A. Koptelov, 2015, published in Poverkhnost’. Rentgenovskie, Sinkhrotronnye i Neitronnye Issledovaniya, 2015, No. 3, pp. 5–10.
Alexeev, A.A., Sadykov, R.A., Litvin, V.S. et al. J. Synch. Investig. (2015) 9: 215. https://doi.org/10.1134/S1027451014060202
© 2015, Pleiades Publishing, Ltd. The results of experiments on the formation and investigation of thin film Al2O3 coatings grown via atomic-layer deposition onto beryllium components for X-ray optics applications are detailed. The chemical properties and the structural and phase compositions of coated samples prior to and after exposure to a monochromatic and nonmonochromatic (“white”) synchrotron radiation with a power of up to 1 kW are studied. Approbation demonstrated the high durability of coatings exposed to an intense beam and the prevention of the penetration of unbound beryllium particles to the surface.
Original Russian Text © O.V. Yurkevich, K.Yu. Maksimova, A.Yu. Goikhman, A.A. Snigirev, I.I. Snigireva, 2015, published in Poverkhnost’. Rentgenovskie, Sinkhrotronnye i Neitronnye Issledovaniya, 2015, No. 3, pp. 34–39.
Yurkevich, O.V., Maksimova, K.Y., Goikhman, A.Y. et al. J. Synch. Investig. (2015) 9: 243. https://doi.org/10.1134/S1027451015020202
On the use of a ZrOx-SiO2 multilayer structure as a test sample for high-resolution X-ray microscopy
© 2015, Pleiades Publishing, Ltd. An image of a ZrOx-SiO2 multilayer structure with a magnification factor of 46, recorded in the mode of high-resolution transmission electron microscopy, and the absorption profile of the multilayer structure, recorded by scanning X-ray microscopy, are obtained using X-ray compound refractive lenses (CRL). Based on these results, a conclusion can be drawn regarding the possibility of using the multilayer structure as a universal test object for high-resolution X-ray microscopy.
Medvedeva, S.S., Lyatun, I.I., Ershov, P.A. et al. J. Synch. Investig. (2015) 9: 341. https://doi.org/10.1134/S1027451015020354
Linear and nonlinear dielectric properties of BaTiO3/Si film heterostructures prepared by pulsed laser deposition
Heterojunctions consisting of n-BaTiO3 films 70 nm thick and p-silicon substrates with orientation (100) were fabricated by pulsed laser deposition. It was shown based on linear and nonlinear dielectric measurements that three sequential structural transitions between the cubic, tetragonal, orthorhombic, and rhombohedral phases with parameters somewhat differing from parameters of corresponding transitions in the BaTiO3 single crystal occur in barium titanate films. The geometry of dielectric measurements differed when revealing particular phase transitions. A considerable increase in the heterojunction nonlinearity upon the transition of the film into the ferroelectric state was observed.
Baryshnikov, S.V., Charnaya, E.V., Meredelina, T.A. et al. Phys. Solid State (2015) 57: 395. https://doi.org/10.1134/S1063783415020043
© 2014 IEEE.In this paper, we studied magnetic properties of Heusler-type glass-covered microwires and thin films. The results have shown that we succeeded to prepare Ni-Mn-In thin films and Ni-Mn-Ga and Ni-Mn-In microwires that have martensitic and austenitic phases at room temperature.
Zhukova, Valentina, et al. "Effect of annealing on magnetic properties and Giant magnetoimpedance effect of amorphous microwires." IEEE Transactions on Magnetics 50.6 (2014): 1-4
The voltage generated in a noncentrosymmetric crystal due to the bulk photovoltaic effect (BPE) can greatly exceed the energy gap, however, the light energy conversion efficiency is extremely low. Here we show that the BPE is remarkably enhanced in the case of thin films. The measurements of the BPE in heteroepitaxial single domain ferroelectric BaTiO3 thin films reveal the enhancement of both photoinduced electric field and conversion efficiencies of the BPE by more than 4 orders of magnitude. Besides the fundamental aspect, our results indicate the potential for the use of the BPE in photovoltaic applications. ©2014 American Physical Society
A. Zenkevich et. al. "Giant bulk photovoltaic effect in thin ferroelectric BaTiO3 films" Phys. Rev. B 90, 161409(R); https://doi.org/10.1103/PhysRevB.90.161409
Coexistence of long range magnetic order and intervalent state of Eu in EuCu2(Si x Ge1 − x )2: Evidence from neutron diffraction and spectroscopic studies
Experimental results of the X-ray absorption spectroscopy, Mossbauer spectroscopy (isomer shift) and neutron diffraction are presented for the series of EuCu2(Si (x) Ge1 - x )(2) polycrystalline samples (0 < x < 0.75). Homogeneous intermediate valence state is established for Eu ions as well as long range magnetically ordered state at the temperatures below 10-15 K. Observation of the ordered magnetic moments at Eu site gives rise to the experimental statement for the coexistence of valence fluctuations and long range magnetic order takes place in the wide range of Ge concentrations for this substance.
Alekseev, P.A., Nemkovski, K.S., Kozlenko, D.P. et al. Jetp Lett. (2014) 99: 164. https://doi.org/10.1134/S0021364014030023
The Particles Precipitation and Osseointegration of a TiO2 Thin-Film Coating by Ion Beam Deposition - An In vivo Study
© 2014 Bogdanov E, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Bogdanov E, Vavilina Y, Shusharina N, Goykhman A, Patrushev M (2014) The Particles Precipitation and Osseointegration of a Tio2 Thin-Film Coating by Ion Beam Deposition - An In vivo Study. J Nanomed Nanotechnol 5:189. doi:10.4172/2157-7439.1000189
Thermoelectric composite materials based on intermediate-valence cerium and ytterbium intermetallic compounds
An important thermoelectric characteristic-the power factor of composite thermoelectric materials—is calculated on the basis of performed measurements of the thermopower, electric conductivity, thermal conductivity, and reference data. The investigated composites consist of intermediate-valence CeNi and YbAl3 intermetallic systems and elementary metals, nickel and chromium. On account of the specific transport properties of a heterogeneous medium, it becomes possible to increase the value of the power factor in composites at a sufficiently low concentrations of rare-earth-element-based intermetallic compounds. The dependences of the composite-thermoelectric-material power factor on the temperature and the mass fraction of valence-instable components are obtained.
Original Russian Text © D.N. Trunov, E.S. Clementyev, 2014, published in Poverkhnost’. Rentgenovskie, Sinkhrotronnye i Neitronnye Issledovaniya, 2014, No. 1, pp. 39–43
Trunov, D.N. & Clementyev, E.S. J. Synch. Investig. (2014) 8: 35. https://doi.org/10.1134/S1027451014010182
Two types of asymmetry in giant magnetoresistance (GMR) are observed which are not related to a training effect, but indicate different mechanisms of magnetization reversal of the pinned layer in spin-valve (SV) structures for ascending and descending field scans. GMR, exchange bias and coercivity in Si/Ta/NiFe/Cu/NiFe/IrMn/Ta SV-structures were investigated as functions of the thickness of the nonmagnetic spacer. The spacer thickness effects are discussed in correlation with layers microstructure and interfaces morphology variations. © 2014 Springer Science+Business Media New York.
Chechenin, N.G., Chernykh, P.N., Dushenko, S.A. et al. J Supercond Nov Magn (2014) 27: 1547. https://doi.org/10.1007/s10948-013-2473-0
X-ray refractive lenses are proposed as a Fourier transformer for\nhigh-resolution X-ray crystal diffraction. By employing refractive\nlenses the wave transmitted through the object converts into a spatial\nintensity distribution at its back focal plane according to the\nFourier-transform relations. A theoretical consideration of the\nFourier-transform technique is presented. Two types of samples were\nstudied in Bragg reflection geometry: a grating made of strips of a thin\nSiO2 film on an Si substrate and a grating made by profiling an Si\ncrystal. Fourier patterns recorded at different angles along the rocking\ncurves of the Si 111 Bragg reflection were analysed. (C) 2013\nInternational Union of Crystallography Printed in Singapore - all rights\nreserved
P. Ershov et. al. "Fourier crystal diffractometry based on refractive optics", J. Appl. Cryst. (2013). 46, 1475-1480
Refractive optics is proposed as a Fourier transformer for high\nresolution X-ray crystal diffraction. Employing refractive lenses the\nwave transmitted through the object transforms into spatial intensity\ndistribution at its back focal plane according to the Fourier relations.\nA theoretical consideration of the Fourier transform technique is\npresented. Two types of samples were studied in Bragg reflection\ngeometry: a grating made of strips of a thin SiO2 film on Si substrate\nand a grating made by profiling a Si crystal. Rocking curves of Si(111)\nBragg reflection and corresponding Fourier patterns were analyzed. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
P. Ershov, S. Kuznetsov, I. Snigireva, V. Yunkin, A. Goikhman, A. Snigirev, "X-ray refractive optics as a Fourier transformer for high resolution diffraction", Proc. SPIE 8777, Damage to VUV, EUV, and X-ray Optics IV; and EUV and X-ray Optics: Synergy between Laboratory and Space III, 877716 (3 May 2013)
Electroresistance in ferroelectric tunnel junctions is controlled by changes in the electrostatic potential profile across the junction upon polarization reversal of the ultrathin ferroelectric barrier layer. Here, hard X-ray photoemission spectroscopy is used to reconstruct the electric potential barrier profile in as-grown Cr/BaTiO3(001)/Pt(001) heterostructures. Transport properties of Cr/BaTiO3/Pt junctions with a sub-μm Cr top electrode are interpreted in terms of tunneling electroresistance with resistance changes of a factor of ∼30 upon polarization reversal. By fitting the I-V characteristics with the model employing an experimentally determined electric potential barrier we derive the step height changes at the BaTiO3/Pt (Cr/BaTiO3) interface +0.42(−0.03) eV following downward to upward polarization reversal.
A. Zenkevich et. al. "Electronic band alignment and electron transport in Cr/BaTiO3/Pt ferroelectric tunnel junctions", Appl. Phys. Lett. 102, 062907 (2013); https://doi.org/10.1063/1.4792525
Change in the magnetic properties of polycrystalline thin-film magnetite upon introduction of an iron sublayer
The field dependences of the magnetic moment of polycrystalline magnetite films formed by pulsed laser deposition on a silicon substrate with the addition of an iron sublayer have been investigated. The influence of the sequence of layers Fe/Fe 3 O 4 and Fe 3 O 4 /Fe on the magnetic characteristics of these structures has been analyzed. It has turned out that an increase in the saturation magnetization and the formation of a rectangular hysteresis loop with the coercive force acceptable for applications of thin-film magnetite as a hard magnetic electrode of the magnetic tunnel junction are observed only for the sequence of layers Fe/Fe 3 O 4 . The effect of the vacuum annealing temperature on the magnetic properties of polycrystalline samples of the Fe/Fe 3 O 4 structure has been studied. It has been found that the best result is achieved at an annealing temperature of 500°C. The phenomenological model describing the magnetic properties of the polycrystalline two-layer magnetic structure Fe/Fe 3 O 4 has been formulated. The results of numerical calculations have demonstrated that the introduction of only two phenomenological anisotropic interactions into the expression for the energy of the film provides a qualitative description of the observed experimental data in the form of hysteresis loops. © 2012 Pleiades Publishing, Ltd.
Anisimov, A.V., Goikhman, A.Y., Kupriyanova, G.S. et al. Phys. Solid State (2012) 54: 1153
We report on the results of the magnetic and structure properties investigation of Heusler alloy films. Ni-Mn-In thin films were formed by pulsed laser deposition. Stoichiometry was varied and controlled by co-deposition technique. The different deposition conditions and influence of the annealing temperature on the film composition were investigated using Auger electron spectroscopy and Rutherford backscattering spectrometry. The optimal annealing temperature was found to be 620 K. The set of the films deposited on the oxidized Si (100) substrate at room temperature and annealed at 620 K was investigated using X-ray diffractometry at room temperature and Vibrating sample magnetometery at low temperatures. The crystal structure was found to be a mixture of austenitic and martensitic phases at room temperature. Decreasing of Curie temperature from 270 K to 250 K with the decreasing of In concentration from 20 at % to 15 at % was observed.
A. Grunin et al., "Ni-Mn-In Heusler Alloy Thin Films Grown by Pulsed Laser Deposition", Solid State Phenomena, Vol. 190, pp. 311-314, 2012
Properties of silicon dioxide layers with embedded metal nanocrystals produced by oxidation of Si:Me mixture
A two-dimensional layers of metal (Me) nanocrystals embedded in SiO2 were produced by pulsed laser deposition of uniformly mixed Si:Me film followed by its furnace oxidation and rapid thermal annealing. The kinetics of the film oxidation and the structural properties of the prepared samples were investigated by Rutherford backscattering spectrometry, and transmission electron microscopy, respectively. The electrical properties of the selected SiO2:Me nanocomposite films were evaluated by measuring C-V and I-V characteristics on a metal-oxide-semiconductor stack. It is found that Me segregation induced by Si:Me mixture oxidation results in the formation of a high density of Me and silicide nanocrystals in thin film SiO2 matrix. Strong evidence of oxidation temperature as well as impurity type effect on the charge storage in crystalline Me-nanodot layer is demonstrated by the hysteresis behavior of the high-frequency C-V curves. © Novikau et al; licensee Springer. 2011
The Ion Beam Deposition (IBD) technique is not very widespread, but simple and very powerful methodic of thin film preparation, allowing to obtain high quality, smooth and very uniform films on big substrate areas (until 40 cm diameter), by target ablation with high energy particles in high vacuum. For the bombarding of the target is convenient to use the charged particles - ions of Ar, because they are easy to disperse in the electric field. Also, including neutralizing system, allow to obtain high-energy neutrals, irradiating the target, producing thin films from any kind of solid targets: from simple metals to complex conducting and non-conducting stoichiometric alloys. Thus, energy of condensing target particles is an average from several units to tens of eV. In the present contribution, we discuss the possibilities and advantages of IBD technology on application examples, including results of functional properties research of Ti, TiO 2 , SiO 2 and Ag thin films for medicine applications, Ni, NiOx, Co and CoO single layers and structures for spintronics applications, and TiO 2 -SiO 2 , Ti-Zr-O-SiO 2 multilayer structures for laser mirrors applications, produced by IBD system. Good structural, morphological quality (with roughness ∼ 0.3 nm) and high uniformity on big areas along with right phase and stoichiometric state is demonstrated by convenient standard techniques for the structures prepared under the optimized growth conditions. © (2011) Trans Tech Publications, Switzerland.
A.Y. Goikhman et al., "Ion Beam Deposition for Novel Thin Film Materials and Coatings", Materials Science Forum, Vol. 674, pp. 195-200, 2011