The microscopic origin of ultrafast modification of the ratio between the symmetric (J) and antisymmetric (D) exchange interaction in antiferromagnetic iron oxides is revealed, using femtosecond ...laser excitation as a pump and terahertz emission spectroscopy as a probe. By tuning the photon energy of the laser pump pulse we show that the effect of light on the D/J ratio in two archetypical iron oxides FeBO3 and ErFeO3 is maximized when the photon energy is in resonance with a spin and parity forbidden d − d transition between the crystal-field split states of Fe3+ ions. The experimental findings are supported by a multielectron model, which accounts for the resonant absorption of photons by Fe3+ ions. Our results reveal the importance of the parity and spin-change forbidden, and therefore often underestimated, d − d transitions in ultrafast optical control of magnetism.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
This review describes the structure and functions of Y-box binding protein 1 (YB-1) and its homologs. Interactions of YB-1 with DNA, mRNAs, and proteins are considered. Data on the participation of ...YB-1 in DNA reparation and transcription, mRNA splicing and translation are systematized. Results on interactions of YB-1 with cytoskeleton components and its possible role in mRNA localization are discussed. Data on intracellular distribution of YB-1, its redistribution between the nucleus and the cytoplasm, and its secretion and extracellular functions are summarized. The effect of YB-1 on cell differentiation, its involvement in extra- and intracellular signaling pathways, and its role in early embryogenesis are described. The mechanisms of regulation of
YB-1
expression in the cell are presented. Special attention is paid to the involvement of YB-1 in oncogenic cell transformation, multiple drug resistance, and dissemination of tumors. Both the oncogenic and antioncogenic activities of YB-1 are reviewed. The potential use of YB-1 in diagnostics and therapy as an early cancer marker and a molecular target is discussed.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The effect of the high pressure on the electronic properties of NiO is studied within the multielectron approach. The low energy physics is described by the effective Hubbard model based on Ni
d
...-electrons and O
p
-electrons in three charge sectors of the Hilbert space: neutral states (configurations
d
8
+
d
9
L +
d
10
L
2
), electron removal states (configurations
d
7
+
d
8
L +
d
9
L
2
), and electron addition states (
d
9
+
d
10
L) with L denotes a ligand hole. Due to a high spin (HS)-low spin (LS) crossover in the electron removal states at pressure
P
S
determined by a competition of the intraatomic Hund exchange interaction and increasing with pressure crystal field 10Dq, the effective Hubbard parameter
U
eff
and the insulator gap
E
g
depend on pressure. We find weak increasing of
E
g
for
P
<
P
S
and weak decreasing
E
g
for
P
>
P
S
. The Mott-Hubbard transition pressure is estimated to be in the interval 450–650 GPa.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•New oxyborate Co5/3Nb1/3BO4 was grown using the flux technique.•Crystal structure has been resolved in details.•The compound undergoes two magnetic transitions at TN1 = 27 K and TN2 = 14 K.
...Needle-shape single crystals of Co5/3Nb1/3BO4 warwickite were grown using the flux technique. X-ray diffraction measurements have revealed an orthorhombic structure (Sp. Gr. Pbnm) where the octahedral M1 site is occupied by a mixture of Co2+/Nb5+ ions and the M2 site is exclusively filled by Co2+ ions. Using dc magnetization measurements it was established that the new material undergoes two magnetic transitions: an antiferromagnetic transition at TN1 = 27 K and a ferrimagnetic one at TN2 = 14 K, below which a hysteresis cycle opens. Both magnetic transitions are marked by anomalies in the specific heat. High magnetic anisotropy with c-axis as a hard magnetization direction was detected.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A spin-crossover mechanism in ludwigite Со
3
BO
5
is proposed on the basis of the DFT calculation with SCAN potentials. The role of separate exchange interactions in the establishment of the ...long-range magnetic order is demonstrated within the Monte Carlo method.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Electron-phonon coupling, diagonal in a real space formulation, leads to a polaron paradigm of smoothly varying properties. However, fundamental changes, namely the singular behavior of polarons, ...occur if off-diagonal pairing is involved into consideration. The study of polaron transformations and related properties of matter is of particular interest for realistic models, since competition between diagonal and off-diagonal electron-phonon contributions in the presence of other strong interactions can result in unconventional behavior of the system. Here we consider a two-dimensional multiband p d model of cuprate superconductors with electron-phonon interaction and analyze the features of the systems that are caused by the competition of diagonal and off-diagonal electron-phonon contributions in the limit of strong electron correlations. Using the polaronic version of the generalized tight-binding method, we describe the evolution of the band structure, Fermi surface, density of states at Fermi level, and phonon spectral function in the space of electron-phonon parameters ranging from weak to strong coupling strength of the adiabatic limit. On the phase diagram of polaron properties we reveal two quantum phase transitions and show how electron-phonon interaction gives rise to Fermi surface transformation (i) from hole pockets to true Fermi arcs and (ii) from hole to electron type of conductivity. We also demonstrate the emergence of new states in the phonon spectral function of the polaron and discuss their origin.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The 90° and 180° super-exchange interaction in the Mott–Hubbard dielectrics NiO and CoO under normal conditions and at high hydrostatic pressure, which leads to spin crossover on magnetic ions, is ...estimated. It is shown that the magnetic ordering in these materials is completely determined by the 180° super exchange in the second coordination shell.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•The magnetic structures of Fe3BO5 and Co3BO5 ludwigites have been studied experimentally and theoretically.•The different collinear spin configurations in the triads 3-1-3 and 4-2-4 have been ...considered.•In Fe3BO5 the heavy frustrations of superexchange interactions between the 3-1-3 and 4-2-4 spin ladders have been found.•In Co3BO5 the frustrations are quenched for a Co3+ low spin state.
The magnetic structures of Fe3BO5 and Co3BO5 ludwigites have been studied experimentally by magnetic measurements and theoretically by the combination of the group theoretical analysis and semi empiric calculations of the superexchange interactions. The different collinear spin configurations in the triads 3-1-3 and 4-2-4 including ferromagnetic, antiferromagnetic and dimer have been considered. For Fe3BO5 the antiferromagnetic state with zero magnetic moment per unit cell, showing the lowest energy, results to be the most probable magnetic ground state. The unusual magnetic structure comprising two virtually independent orthogonal subsystems is formed to avoid heavy frustrations of superexchange interactions between the 3-1-3 and 4-2-4 spin ladders. In Co3BO5 the magnetic frustrations present for the Co3+ high-spin state are quenched for a Co3+ low spin state resulting in the ferrimagnetic long-range order. The obtained results are discussed in comparison with experimental magnetic data.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This book provides the first systematic discourse on a very peculiar approach to the theory of strongly correlated systems. Hubbard X-operators have been known for a long time but have not been ...widely used because of their awkward algebra. The book shows that it is possible to deal with X-operators even in the general multilevel local eigenstate system, and not just in the case of the nondegenerate Hubbard model. X-operators provide the natural language for describing quasiparticles in the Hubbard subbands with unusual doping and temperature-dependent band structures.The X-operator diagram technique is presented in detail, so that a newcomer with knowledge of the usual Fermi/Bose operator diagram technique can use the former after reading the book.Examples are taken from the theory of high-Tc superconductivity, rare-earth compounds with strong magnetic anisotropy and quantum oscillations in strongly correlated systems.
Features of the formation of the magnetic structure and the exciton Bose–Einstein condensate phase of magnetic excitons in strongly correlated systems near the spin crossover have been considered ...with the effective Hamiltonian obtained from the two-band Hubbard–Kanamori model. The coexistence of antiferromagnetism and exciton condensate, as well as the appearance of the long-range excitonic antiferromagnetic order even in the absence of the interatomic exchange interaction, has been revealed. The role of the electron–phonon coupling has been considered.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
PDF
