Vadim V. Sikolenko

Vadim V. Sikolenko
Karlsruhe Institute of Technology | KIT · Institute of Applied Geosciences

Dr.

About

186
Publications
11,508
Reads
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1,516
Citations
Additional affiliations
January 2011 - present
Karlsruhe Institute of Technology
Position
  • Researcher
Description
  • Epsilon-project responsible
August 2010 - December 2010
Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Position
  • Researcher
June 2008 - July 2010
Paul Scherrer Institut
Position
  • Researcher

Publications

Publications (186)
Preprint
Full-text available
Sm-doped BiFeO3 compacted powders with composition across the morphotropic phase boundary region were prepared by sol-gel method. Crystal structure, morphology and magnetic state of the compounds were analyzed as a function of dopant concentration, temperature and external pressure using synchrotron and laboratory X-ray diffraction, electron micros...
Article
Sm-doped BiFeO3 compacted powders with composition across the morphotropic phase boundary region were prepared by sol-gel method. Crystal structure, morphology and magnetic state of the compounds were analyzed as a function of dopant concentration, temperature and external pressure using synchrotron and laboratory X-ray diffraction, electron micros...
Article
We studied structural and magnetic phase transitions under applied pressure for the doped cobaltite La0.75Ba0.25CoO2.9. Neutron and x-ray diffraction experiments established the coexistence of rhombohedral and cubic phases in the sample. The magnetic state at 2 K is best described as a long-range ordered antiferromagnet (AFM) with small ferromagnet...
Article
Full-text available
The crystal structure of BiMnO3+δ ceramics has been studied as a function of nominal oxygen excess and temperature using synchrotron and neutron powder diffraction, magnetometry and differential scanning calorimetry. Increase in oxygen excess leads to the structural transformations from the monoclinic structure (C2/c) to another monoclinic (P21/c),...
Preprint
A correlation between the crystal structure and magnetic properties of system (1-x)BiFeO$_3$-(x)BaTiO$_3$ with compounds across the morphotropic phase boundary was studied using X-ray and neutron diffraction, magnetometry, and Mossbauer spectroscopy measurements. Increase in the dopants content leads to the structural transition from the rhombohedr...
Article
A correlation between the crystal structure and magnetic properties of system (1-x)BiFeO3 – (x)BaTiO3 with compounds across the morphotropic phase boundary was studied using X-ray and neutron diffraction, magnetometry, and Mössbauer spectroscopy measurements. Increase in the dopants content leads to the structural transition from the rhombohedral p...
Article
Full-text available
Transition metal oxides are promising electrocatalysts for water oxidation, i.e., the oxygen evolution reaction (OER), which is critical in electrochemical production of non-fossil fuels. The involvement of oxidation state changes of the metal in OER electrocatalysis is increasingly recognized in the literature. Tracing these oxidation states under...
Article
Full-text available
The work is focused on the thermal expansion of composites based on valence-unstable systems. The main motivation was to create invar-like materials of a new type and to develop approaches to the quantitative description of coefficients of thermal expansion (CTE) of both the composite itself and its key component - a material with a negative contri...
Article
Full-text available
(This is an open access paper.) High-pressure synthesized quasi-one-dimensional NaMn 2 O 4 and Li 0.92 Mn 2 O 4 are both antiferromagnetic insulators. Here their atomic and magnetic structures are investigated using neutron powder diffraction. The present crystal structural analyses of NaMn 2 O 4 reveal that a Mn 3+ /Mn 4+ charge-ordering state exi...
Preprint
The high-pressure synthesised quasi-one-dimensional compounds NaMn2O4 and Li0.92Mn2O4 are both antiferromagnetic insulators, and here their atomic and magnetic structures were investigated using neutron powder diffraction. The present crystal structural analyses of NaMn2O4 reveal that Mn3+/Mn4+ charge-ordering state exist even at low temperature (d...
Article
Many nanofabrication processes require sophisticated equipment, elevated temperature, vacuum or specific atmospheric conditions, templates, and exotic chemicals, which severely hampers their implementation in real-world applications. In this study, we outline a fully wet-chemical procedure for equipping a 3D carbon felt (CF) substrate with a multif...
Article
The unconventional transport and magnetic properties of perovskitelike lanthanum cobalt oxide LaCoO 3 have been studied for more than five decades. This highly correlated electron system exhibits a variety of peculiar properties that are desirable for environmentally friendly energy solutions, fuel cell technologies, novel diesel engines, and oxyfu...
Article
The structural parameters of the Bi0.85AE0.15Fe0.85Ti0.15O3 (AE = Ca and Ba) multiferroics have been determined using variable temperature neutron powder diffraction. The compounds adopt the polar rhombohedral R3c structure near room temperature and undergo phase transitions into either the nonpolar orthorhombic Pnma (AE = Ca) or cubic Pm3-m (AE =...
Article
Crystal structure of the Bi1-xBaxFe1-xTixO3 ceramics across the phase boundary region between the polar rhombohedral and pseudo-cubic phases has been investigated by means of X-ray and neutron diffraction, scanning electron microscopy and differential scanning calorimetry techniques. The structural measurements have revealed a decrease in the rhomb...
Article
Having been considered as materials of exceptional technological importance, magnetoelectric multiferroics continue to attract tremendous research interest. While the steady progress achieved in this field over the past decades has made our understanding of underlying physics substantially exhaustive and deep, some topics still remain to be debated...
Article
The crystal structure and magnetotransport properties of stoichiometric and anion-deficient Ba²⁺‑alloyed cobaltites with a perovskite structure have been studied. It was shown that the development of ferromagnetic state is related to the presence of cobalt ions mainly with single eg electron (intermediate spin IS state), whereas the existence of tw...
Article
The dependence of the properties of the La0.45Ba0.55CoO3 – δ and La0.4Ba0.6CoO3 – δ cobaltites on the oxygen content has been studied. A decrease in the oxygen content leads to the stabilization of cobalt ions in the 3+ oxidation state and to a transition from a conducting state with positive exchange interaction to an antiferromagnetic insulating...
Article
The crystal structures of Bi1 – xPrxFeO3 solid solutions in the vicinity of the transition from the polar rhombohedral phase to the nonpolar orthorhombic phase have been analyzed by X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. These methods made it possible to reveal the specific features of the change...
Article
Investigation of the crystal structure, magnetic and transport properties of both the stoichiometric and anion-deficient Ba²⁺-doped lanthanum cobaltites was performed. Anomalous temperature behavior of the structural parameters as well as the magnetic, electrical and magnetotransport characteristics was found due to concurrence of magnetic interact...
Article
Sr1-xYxCoO2.65 (x = 0.2) with layered perovskite structure was studied by neutron diffraction, synchrotron x-ray and magnetometry methods. It is shown that in the 90-375 K temperature range the crystal structure can be described by the monoclinic space group A2/m with the superstructure 4√2a p × 2√2a p × 4a p (with a p corresponding to the unit cel...
Article
Compositional and temperature evolution of crystal structure and magnetic properties of the BiFeO3-based compounds co-doped with Ca and transition metal ions - Mn, Ti or Nb was studied with X-ray diffraction and vibrating sample magnetometer techniques. It has been shown that the chemical substitution allows to vary structural parameters, thus modi...
Article
The structure, the magnetic and magnetotransport properties of perovskite Sr0.9Y0.1CoO2.63 have been studied. The sample is shown to have a two-phase structure. The main phase has a tetragonally distorted unit cell and is described by space group I4/mmm. The broadening of the reflections with indices corresponding to doubling unit cell parameter c...
Article
The results of neutron-diffraction, magnetic, and magnetotransport studies of La1 ‒ xSrx(Mn 3+1- x/2Sb 5+x/2)O3 (x ≤ 0.7) pervoskites, which contain only Mn3+ ions, are reported. It is demonstrated that the system undergoes a transition from the antiferromagnetic state to the ferromagnetic one at x ∼ 0.2. Its structure then changes from O′-orthorom...
Article
The evolution of crystal structure and piezoelectric properties of the Bi1-xSmxFeO3 ceramics with compositions corresponding to the phase boundary region between the polar rhombohedral and anti-polar orthorhombic phases have been studied. The materials have been investigated using X-ray diffraction, transmission electron microscopy and piezorespons...
Article
The evolution of the magnetic and magnetotransport properties and of the crystal structure in the cobaltites La0.45Ba0.55CoO3‐δ and La0.4Ba0.6CoO3‐δ depending on the oxygen content is investigated by various methods. The oxygen content decrease leads to a stabilization of the oxidation state 3+ of the cobalt ions and to a transition from ferromagne...
Article
Neutron diffraction, magnetic and magnetotransport studies of perovskites R1-x³⁺Srx²⁺ (Mn1-x³⁺ Sbx/ 2⁵⁺ )O3 (R = La, Pr) were carried out. It is shown that for x ∼ 0.2 systems undergo a transition from an antiferromagnetic state (x=0) to a ferromagnetic state. In the case of the R=La series a structural transformation from theO?-orthorhombic phase...
Article
La0.7Sr0.3Mn1 – xNix O3 (0.12 ≤ x ≤ 0.35) compositions have been studied using neutron diffraction, magnetometry, and measurements of magnetotransport properties. At temperatures of 5–300 K, these compounds were found to have a rhombohedral crystal structure. The substitution of nickel for manganese has been shown to result in a decrease in the Cur...
Article
Having been considered as a prime example of a room-temperature magnetoelectric multiferroic, BiFeO3 continues to attract much interest. Since functional properties of this material can be effectively influenced by chemical, electrical, magnetic, mechanical and thermal stimuli, it can serve as a model for the investigation of cross-coupling phenome...
Article
Spin transitions of cobalt ions in LaCoO3 single crystals have been studied by the method of X-ray magnetic circular dichroism (XMCD) at the K- and L2,3-edges of Co³⁺ ions. The orbital momentum of cobalt ions obtained for the K-edge at the 3d level in the region of the spin transition in the temperature range from 25 to 120 K increases by a factor...
Article
X-ray diffraction and inelastic X-ray scattering studies have been performed across the spin (~100K) and semiconductor-metal (~500K) transitions in LaCoO3 single crystals. The quadratic increase with temperature of the oxygen displacement parameters parallel and perpendicular to the Co-O bond has been correlated with softening of the TO2 and harden...
Article
The crystal structure and magnetic properties of polycrystalline compounds La0.7Sr0.3Mn1−x Nix O3 (x ≤ 0.37) were studied by neutron powder diffraction and magnetometry measurements, and the magnetotransport properties were also investigated, focusing on the magnetic state of the compounds. The crystal structure of the compounds remains rhombohedra...
Article
Correlations between local and long-range structure distortions in the perovskite-type RE 1-xSrxCoO3-δ (RE = La, Pr, Nd; x = 0.0 and 0.5) compounds have been studied at room temperature by extended X-ray absorption fine structure (EXAFS) at the Co K-edge and high-resolution neutron powder diffraction (NPD). The use of two complementary experimental...
Article
La1-xSrxMn0.5S(cyrillic)o0.5O3 (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...
Article
Full-text available
Crystal structure of the Bi1−xPrxFeO3 ceramics of the compositions corresponding to the threshold concentrations separating the polar rhombohedral (R3c) and anti-polar orthorhombic (Pbam) phases has been investigated with X-ray diffraction, transmission electron microscopy and differential scanning calorimetry measurements performed in a broad temp...
Article
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 o...
Article
The compositions La0.7Sr0.3Mn1 – xCoxO3 (0.13 ≤ x ≤ 1) are studied by neutron diffraction, magnetometry, and measuring the magnetotransport properties. The substitution of cobalt ions for manganese ions is shown to decrease the magnetization and the Curie temperature from 270 K (x = 0.13) to 140 K (x = 0.33). As the cobalt ion content increases to...
Article
A combined diffraction and EXAFS study of LaCoO3 and La0.5Sr0.5Co0.75Nb0.25O3 powders — CORRIGENDUM - E. A. Efimova, V. V. Sikolenko, D. V. Karpinsky, I. O. Troyanchuk, S. Pascarelli, C. Ritter, M. Feygenson, S. I. Tiutiunnikov, V. Efimov
Article
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...
Article
The system of La1–xSrxCo0.5Mn0.5O3 solid solutions have been studied by neutron diffraction and the measurement of the magnetization. The composition with x = 0 has the monoclinic structure (space group P21/n); the compositions with 0.15 ≤ x ≤ 0.6 are rhombohedral (R\(\bar 3\)c), and the composition with x = 0.75 is cubic (Pm\(\bar 3\)m). All the c...
Article
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 LaCoO 3 and La 0.5 Sr 0.5 Co 0.75 Nb 0.25 O 3 . The analysis of t...
Article
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 LaCoO 3 and LaGaO 3 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...
Chapter
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 h...
Article
Anion-deficient La0.5Ba0.5CoO2.8 and Y0.25Ca0.25Sr0.5CoO2.62 cobaltites are studied under pressures up to 6.5 GPa in the temperature range of 5−300 K by neutron powder diffraction. Under ambient pressure both compounds are antiferromagnetic with TN = 250 K. The applied pressure induces in the first compound a gradual transition from the antiferroma...
Article
Full-text available
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 transitio...
Article
The crystal structure and piezoelectric and magnetic properties have been studied in Bi1‒xSmxFeO3 solid solutions with the compositions near the morphotropic boundary between rhombohedral and orthorhombic (Rh–Orh) phases. The coexistence areas of rhombohedral and antipolar orthorhombic phases, as well as the evolution of structural phases at the in...
Article
The crystal and magnetic structure of the La0.75Ba0.25CoO3 has been studied as a function of temperature and high pressure up to 8 GPa using neutron powder diffraction. The crystal structure of the compound at room temperature is considered to be single phase rhombohedral (space group _R__c_), at T = 50 K the crystal structure is described by two-p...
Article
Ceramic samples La1−2xSr2xMn1−xSbxO3 (x≤0.2) have been studied by X-ray and neutron powder diffraction, magnetization measurements and charge density calculations have also been performed. The compounds are characterized by the rhombohedral structure at room temperature; temperature decrease causes structural transition to the orthorhombic structur...
Article
Full-text available
We report on Co K-edge x-ray magnetic circular dichroism (XMCD) measurements of LaCoO3 single crystal in temperature range from 5 to 300 K and external magnetic field of 17 T. The response consists of pre-edge (at 7712 eV) and bi-polar peak (up at 7727, down at 7731 eV) with amplitudes, respectively, less than 10-3 and 10-2 of the Co K-edge jump. U...
Article
Full-text available
A combined high-resolution Co K-edge extended x-ray absorption fine structure (EXAFS) and high-resolution X-ray powder diffraction (XRD) study has been performed to clarify the detail of anomalous behavior of temperature-dependent magnetic susceptibility curve on the LaCoO3 across the spin-state (~120 K) transition. According to XRD analysis, the D...
Article
The crystal structure and magnetic properties for stochiometric La1-2xSr2xMn1-xSbxO3 (0.1 ≤ x ≤ 0.2) compositions with a manganese ions in the 3+ oxidation state are studied. The rhombohedral structure at ambient temperatures transforms at cooling to an orthorhombic one without any signature of orbital ordering. Compositions with x ≤ 0.2 reveal a f...
Article
Bi1-xPrxFeO3 ceramics of the compositions across the rhombohedral-orthorhombic phase boundary have been studied by X-ray diffraction and piezoresponse force microscopy, charge density calculations and transport properties measurements have been performed. Piezoresponse force microscopy measurements revealed considerable increase of the piezorespons...
Article
The crystal structure and magnetic properties of stoichiometric compounds Ln 0.7Sr0.3Mn0.85Sb0.15O3, in which manganese ions are in a trivalent state, have been investigated. No cooperative orbital ordering has been found in the Ln = La composition, but structural parameters of the Ln = Nd composition indicate Jahn-Teller distortions. It has been s...
Article
Magnetic properties and crystal structure of La0.7Sr0.3Mn1-xMexO3 (Me=Ga, Fe, Cr; x<0.3) have been studied by neutron powder diffraction and magnetization measurements. It is shown that substitution of manganese ions by chromium or gallium ions (x=0.3) leads to phase separation into antiferromagnetic and ferromagnetic phases whereas replacement by...
Article
Full-text available
Structural measurements have been performed on the La 0.7 Sr 0.3 Mn 3+ 0.85 Nb 5+ 0.15 O 3 compound with oxidation state of manganese close to +3. The composition undergoes a structural transition from rhombohedral to orthorhombic symmetry below room temperature. The calculated structural parameters show that the orthorhombic phase is not long-rang...
Article
The magnetization and the crystal structure of the La0.7Sr0.3Mn1 − x Mx O3 (M = Ga, Fe, Cr; x ≤ 0.3) systems are studied. The substitution of gallium and chromium is shown to cause phase separation into antiferromagnetic and ferromagnetic phases, whereas the substitution of iron for manganese stabilizes a spinglass state. The ferromagnetic phase in...
Article
Structural and magnetization measurements have been performed on the La0.7Sr0.3Mn0.85 O3 stoichiometric compounds. With rise of the Mg2+ content the formal oxidation state manganese increases from +3 up to +3.55 . The compositions with undergo a structural transition from rhombohedral to orthorhombic symmetry below room temperature whereas and comp...
Article
Full-text available
The layered cobaltite Sr2CaYCo4O10.5 with formal average cobalt oxidation state close to 3+ has been studied as functions of both temperature and pressure up to 4 GPa by neutron powder diffraction (NPD). The crystal structure is shown to have tetragonal symmetry (space group I4/mmm; 2ap × 2ap × 4ap superstructure), and the magnetic structure at amb...
Article
Compound La0.7Sr0.3Mn0.85Nb0.15O3, in which manganese ions are in an oxidation state close to 3+, are studied by neutron diffraction and magnetic measurements. This compound is shown to be a ferromagnet with T C = 145 K and a magnetic moment of 3.1 μB/Mn at T = 10 K. No signs of cooperative orbital ordering are detected. When Mg2+ ions substitute f...
Article
The crystal structure of solid solutions in the Bi1 − x Pr x FeO3 system near the structural transition between the rhombohedral and orthorhombic phases (0.125 ≤ x ≤ 0.15) has been studied. The structural phase transitions induced by changes in the concentration of praseodymium ions and in the temperature have been investigated using X-ray diffract...
Article
Full-text available
Bi1−x Prx FeO3 ceramics across the rhombohedral–orthorhombic phase boundary have been studied by X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The structural phase transitions in Bi1−x Prx FeO3 driven by doping concentration and temperature are significantly different from those in BiFeO3 compounds dope...
Article
Full-text available
La0.7Sr0.3Mn3+0.85Sb5+0.15O3 and La0.7Sr0.3Mn3+0.8Sb5+0.1Ge4+0.1O3 compounds with dominantly isovalent Mn3+ ions were studied by neutron powder diffraction and magnetization measurements. The compounds are basically ferromagnetic, with magnetic moments slightly above of 3 μB/Mn. Upon temperature decrease, the compounds exhibit structural transition...
Article
We have investigated anomalously slow magnetic domain growth in an antiferromagnetic (AF) phase of isosceles triangular lattice Ising antiferromagnets Co1−xMgxNb2O6 with x=0 and 0.004, by means of time-resolved neutron diffraction measurements. Applying the multi-profile-deconvolution analysis to the observed diffraction profiles, we have revealed...
Article
Bi1−xLaxFeO3 and Bi1−xPrxFeO3 ceramics of the compositions near the morphotropic phase boundary have been studied by X-ray and neutron diffraction techniques and differential thermal analysis. The structural phases characterized by the long-range polar, antipolar, and nonpolar ordering as well as the phase coexistence regions have been identified u...
Article
The crystal structure, piezoelectric and magnetic properties of the Bi1 − x La x FeO3 solid-solution system near the structural transition between the rhombohedral and orthorhombic phases (0.15 ≤ x ≤ 0.2) have been investigated. The regions of existence of the polar rhombohedral and orthorhombic phases have been determined, and the sequence of stru...
Article
The effect of substitution of manganese and niobium for cobalt on the magnetic and crystal structure of doped cobaltites has been studied by the neutron diffraction method. The Pr0.5Sr0.5Co1 − x Mnx O3 samples undergo, with increasing x, a series of transitions of the crystal structure from the monoclinic I2/a to orthorhombic Immm phase, and then,...
Article
The anion deficient cobaltite La0.5Ba0.5CoO2.8 with the formal cobalt valence state close to 3+ has been studied as function of pressure up to 6.5 GPa at different temperatures by neutron powder diffraction. At ambient pressure the crystal structure of this compound has cubic symmetry (space group Pm3̅m) and is found to become antiferromagnetic wit...
Article
Neutron diffraction studies of the La0.5Ba0.5CoO2.8 at the different temperatures has been performed. This solid solution crystallizes in the cubic structure (Pm3m space group) and exhibits below TN ~ 250K G-type antifferomagnetic ordering. Applied pressure suppresses magnetic ordering. Anomalous changes of the lattice parameters under pressure hav...
Article
The evolution of the crystal structure and the magnetic properties was investigated in the La0.5Sr0.5CoO3-δ (0 < δ < 0.3) system as a function of the oxygen deficit δ. Compounds with a low oxygen deficit (δ < 0.1) are shown to be predominantly ferromagnetic, while further increase (δ > 0.1) gradually changes the magnetic structure from ferromagneti...