A5036407093- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Multiferroics and related materials
- Magnetic properties of thin films
- Copper-based nanomaterials and applications
- Cardiac electrophysiology and arrhythmias
- Magneto-Optical Properties and Applications
- Ion channel regulation and function
- Theoretical and Computational Physics
- Cold Atom Physics and Bose-Einstein Condensates
- ZnO doping and properties
- Quantum, superfluid, helium dynamics
- Quantum and electron transport phenomena
- Iron-based superconductors research
- Magnetic Properties and Applications
- Rare-earth and actinide compounds
- Electronic and Structural Properties of Oxides
- Magnetism in coordination complexes
- Neuroscience and Neural Engineering
- Magnetic Properties and Synthesis of Ferrites
- Iron oxide chemistry and applications
- Transition Metal Oxide Nanomaterials
- NMR spectroscopy and applications
- X-ray Diffraction in Crystallography
Ural Federal University
2015-2024
M.N. Mikheev Institute of Metal Physics
1998-2024
Institute of Physics
1998-2021
Lomonosov Moscow State University
1997-2020
Institute of Immunology and Physiology
2005-2015
Russian Academy of Sciences
2012
South Ural State University
2008-2011
Leibniz Institute for Solid State and Materials Research
2003-2009
University of South Wales
1996
Physicotechnical Institute
1993
The optical response of the technologically interesting multiferroic ${\text{BiFeO}}_{3}$ and related complex iron oxides, having high N\'eel or Curie temperature, is studied in wide spectral range from 0.6 up to 5.8 eV by means spectroscopic ellipsometry. investigated oxides have different crystal symmetry with ${\text{FeO}}_{6}$ octahedral ${\text{FeO}}_{4}$ tetrahedral centers distorted a certain degree. One two groups materials includes ${\text{BiFeO}}_{3}$, ${\text{ErFeO}}_{3}$,...
We report on {6,7}Li nuclear magnetic resonance measurements of the spin-chain compound LiCu2O2 in paramagnetic and magnetically ordered states. Below T about 24 K NMR lineshape presents a clear signature incommensurate (IC) static modulation local field consistent with an IC spiral moments. {7}Li reveals strong phason-like dynamical fluctuations extending well below K. hypothesize that series phase transitions at 24.2, 22.5, 9 reflects "Devil's staircase" type behavior generic for systems....
We have performed both theoretical and experimental study of optical response parent perovskite manganites RMnO_3 with a main goal to elucidate nature clearly visible features. Starting simple cluster model approach we addressed the one-center (p-d) two-center (d-d) charge transfer (CT) transitions, their polarization properties, role played by structural parameters, orbital mixing, spin degree freedom. Optical complex dielectric function single crystalline samples (R=La, Pr, Nd, Sm, Eu) was...
A large body of experimental data point towards a charge transfer instability parent insulating cuprates to be their unique property. We argue that the true gap in these compounds is as small 0.4-0.5\,eV rather than 1.5-2.0\,eV usually derived from optical measurements. In fact we deal with competition conventional (3d$^9$) ground state and (CT) formation electron-hole dimers which evolves under doping an unconventional bosonic system. Our conjecture does provide unified standpoint on main...
We report on susceptibility, magnetization, 23Na NMR, and specific heat data of the spin-chain material NaCu2O2 in paramagnetic ordered phases. Below 13 K, where a sharp field-dependent peak appears, NMR lineshape points to an incommensurate static modulation local magnetic field consistent with spiral state Cu moments. At 2 K weak ferromagnetism moment about 4·10− 3μB has been observed. LDA-based estimates exchange integrals reveal large inchain frustration leading spiral.
Nominally pure undoped parent manganite LaMnO_3 exhibits a puzzling behavior inconsistent with simple picture of an A-type antiferromagnetic insulator (A-AFI) cooperative Jahn-Teller ordering. We do assign its anomalous properties to charge transfer instabilities and competition between insulating A-AFI phase metallic-like dynamically disproportionated formally separated by first-order transition at T_{disp}=T_{JT}\approx 750 K. The unconventional high-temperature is addressed be specific...
Luminescence spectra of NiO have been investigated under vacuum ultraviolet (VUV) and soft x-ray (XUV) excitation (DESY, Hamburg). Photoluminescence (PL) show broad emission violet green bands centered at about 3.2 2.6 eV, respectively. The PL (PLE) spectral evolution lifetime measurements reveal that the two mechanisms with short long decay times, attributed to $d({e}_{g})$-$d({e}_{g})$ $p(\ensuremath{\pi})$-$d$ charge transfer (CT) transitions in range 4--6 respectively, are responsible...
The exchange-bias (EB) effect with sign reversal was found in $\mathrm{LuF}{\mathrm{e}}_{0.5}\mathrm{C}{\mathrm{r}}_{0.5}{\mathrm{O}}_{3}$ ferrite-chromite, which is a weak ferrimagnet below ${T}_{\mathrm{N}}=265\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, exhibiting antiparallel orientation of the ferromagnetic (FM) moments Fe and Cr sublattices due to opposite Fe-Cr Dzyaloshinskii vector, as compared that Fe-Fe Cr-Cr. FM studied compound compensate each other at temperature...
We address a systematic microscopic theory of spin-dependent electric polarization in $3d$ oxides starting with generic three-site two-hole cluster. A perturbation scheme realistic for is applied which implies the quenching orbital moments by low-symmetry crystal field, strong intra-atomic correlations, $dp$-transfer effects, and rather small spin-orbital coupling. An effective spin operator electric-dipole moment deduced incorporating both nonrelativistic...
The results of theoretical and experimental studies charge transfer (CT) transitions in multiferroic manganites, ferrites, related insulators are reviewed. Starting with a simple cluster model approach one-center p-d two-center d-d CT transitions, their polarization properties, the role played by structural parameters, orbital mixing, spin degree freedom all addressed. Optical ellipsometry data spectral range 0.6–5.8eV perovskite hexagonal rare-earth manganites RMnO3 orthorhombic RMn2O5...
Disproportionation in 3d compounds can give rise to an unconventional electron-hole Bose liquid with a very rich phase diagram from metal, charge ordering insulator inhomogeneous superfluid.Optimal conditions for the disproportionation driven high-T c superconductivity are shown realize only several Jahn-Teller d n configurations that permit formation of well defined local composite bosons.These high-spin 4 , low-spin 7 and 9 given octahedral crystal field, 1 6 tetrahedral field.The reaction...
We report new results of a 57Fe M\"ossbauer study multiferroic 3R-AgFeO2 powder samples performed in wide temperature range, including two points, TN1 ~ 14 K and TN2 9 K, magnetic phase transitions. At the intermediate < T TN1, spectra can be described terms collinear spin-density-waves (SDW) with inclusion many high-order harmonics, indicating that real structure this ferrite appears to more complicated than pure sinusoidally modulated SDW. The at low temperatures, TN2, consist Zeeman...
Optical response of mixed-valent manganite $\mathrm{Tb}{\mathrm{Mn}}_{2}{\mathrm{O}}_{5}$ is studied in the spectral range from $0.6\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}5.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ order to reveal charge-transfer (CT) transitions responsible for band-gap structure. Strong increase optical $z$ and $y$ polarizations strong anisotropy with a relation ${ϵ}_{2x}<{ϵ}_{2y}<{ϵ}_{2z}$ are found. These findings agree theoretical analysis derived...
We present an overview of the microscopic theory Dzyaloshinskii-Moriya (DM) coupling in strongly correlated 3d compounds. Most attention paper centers around derivation Dzyaloshinskii vector, its value, orientation, and sense (sign) under different types (super)exchange interaction crystal field. consider both Moriya mechanism antisymmetric novel contributions, particular, that spin-orbital on intermediate ligand ions. have predicted a magnetic phenomenon, {\it weak ferrimagnetism} mixed...
High resolution electron energy loss spectroscopy (EELS) measurements of the insulating, layered cuprate compound ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{2}{\mathrm{Cl}}_{2}$ have been performed with a transferred momentum near $\mathbf{k}=0$ and in wide range up to 20 eV. To interpret data semiquantitative embedded cluster approach is applied describe electron-hole excitations insulating cuprates. The theory includes complete set Cu $3d$ O $2p$ orbitals predicts rather $(2\textdiv{}13...
Puzzling multiferroic behavior observed recently in spin-1/2 one-dimensional chain cuprate ${\text{LiCu}}_{2}{\text{O}}_{2}$ with edge-shared arrangement of ${\text{CuO}}_{4}$ plaquettes and incommensurate spiral spin ordering is consistently explained to be a result the nonrelativistic exchange-induced electric polarization on ${\text{Cu}}^{2+}$ centers substituting for positions native ${\text{Cu}}^{1+}$ ions. These substituent are proven an effective probe incommensurability magnetic...
Complex optical dielectric function in the tetragonal rare-earth cuprates ${R}_{2}{\text{CuO}}_{4}$ ($R=\text{La}$, Pr, Nd, and Sm) bismuth cuprate ${\text{Bi}}_{2}{\text{CuO}}_{4}$ is studied spectral range of 0.6--5.4 eV using a method ellipsometry. The spectra are for two main polarizations analyzed terms cluster model ${\text{CuO}}_{4}^{6\ensuremath{-}}$ complexes taking into account intracenter $p\text{\ensuremath{-}}d$ intercenter $d\text{\ensuremath{-}}d$ charge-transfer (CT)...