RAS Institute of Metal Physics

Ekaterinburg, Russia

RAS Institute of Metal Physics

Ekaterinburg, Russia
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Ermolenko A.S.,RAS Institute of Metal Physics
Journal of Magnetism and Magnetic Materials | Year: 2017

Numerical calculations of magnetic properties of Pr3+ ions in crystal field of the mixed (hexagonal + orthorhombic) symmetry in PrNi5− xCux pseudobinary alloys are presented. The molecular field theory and the crystal field theory in the point charge model are used in calculations. It is shown that the admixing of crystal field of orthorhombic symmetry to the original hexagonal crystal field of PrNi5 and PrCu5 compounds leads to an abrupt increase in their magnetic susceptibility followed by the onset of ferromagnetism, which was earlier observed experimentally in pseudobinary PrNi5− xCux alloys. The calculated dependences of magnetic moments of Pr3+ ions in crystal fields of the mixed symmetry on the magnetic field strength and temperature satisfactorily agree with the experimental results for PrNi5− xCux alloys. © 2017 Elsevier B.V.

Popov V.V.,RAS Institute of Metal Physics
Physics of Metals and Metallography | Year: 2012

Grain boundaries of polycrystalline copper have been studied using 57Co( 57Fe) emission Mössbauer spectroscopy. It is shown that Co atoms are diffused over grain boundaries of polycrystalline copper by a vacancy mechanism. The state of Co atoms in the boundary regions of crystallites has been analyzed. The values of coefficients of the grain-boundary segregation of Co in Cu have been determined. © Pleiades Publishing, Ltd., 2012.

Irkhin V.Yu.,RAS Institute of Metal Physics
Journal of Physics Condensed Matter | Year: 2011

A scaling consideration of the Kondo lattices is performed with account of logarithmic Van Hove singularities (VHS) in the electron density of states. The scaling trajectories are presented for different magnetic phases. It is demonstrated that VHS lead to a considerable increase of the non-Fermi-liquid behavior region owing to softening of magnon branches during the renormalization process. Although the effective coupling constant remains moderate, the renormalized magnetic moment and spin-fluctuation frequency can decrease by several orders of magnitude. A possible application to f-systems and weak itinerant magnets is discussed. © 2011 IOP Publishing Ltd.

Bebenin N.G.,RAS Institute of Metal Physics
Physics of Metals and Metallography | Year: 2011

A brief review of properties of the ferromagnetic manganites La 1 - x Ca x MnO3 is given. Lattice properties, magnetic properties, transport phenomena, magnetic resonance, and the results of neutron diffraction and optical studies are considered. Special attention is paid to effects observed near the Curie temperature. © Pleiades Publishing, Ltd., 2011.

Solin N.I.,RAS Institute of Metal Physics
Journal of Experimental and Theoretical Physics | Year: 2012

The nature of the electrical resistivity for low-doped lanthanum manganites is elucidated. The electrical resistivity is described by the Efros-Shklovskii law (inρ ∞ (T 0/T) -1/2, where T 0 ∞ 1/R is) in the temperature range from T* ≈ 300 K ≈ T C (T C is the Curie temperature for conducting manganites) to their T C and is explained by the tunneling of carriers between localized states. The magnetoresistance is explained by a change in the size of localized states R is in a magnetic field. The patterns of change in R is with temperature and magnetic field strength determined from magnetotransport properties are satisfactorily described in the model of phase separation into small-radius metallic droplets in a paramagnetic matrix. The sizes R is and their temperature dependence have been estimated through magnetic measurements. The results confirm the existence of a Griffith phase. The intrinsic inhomogeneities produced by thermodynamic phase separation determine the electrical resistivity and magnetoresistance of lanthanum manganites. © Pleiades Publishing, Inc., 2012.

Solovyev I.V.,Japan National Institute of Materials Science | Pchelkina Z.V.,RAS Institute of Metal Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We present the microscopic theory of improper multiferroicity in BiMnO 3, which can be summarized as follows: (1) the ferroelectric polarization is driven by the hidden antiferromagnetic order in the otherwise centrosymmetric C2/c structure; (2) the relativistic spin-orbit interaction is responsible for the canted spin ferromagnetism. Our analysis is supported by numerical calculations of electronic polarization using the Berry-phase formalism, which was applied to the low-energy model of BiMnO3 derived from the first-principles calculations. We explicitly show how the electric polarization can be controlled by the magnetic field and argue that BiMnO3 is a rare and potentially interesting material where ferroelectricity can indeed coexist and interplay with the ferromagnetism. © 2010 The American Physical Society.

Lyapilin I.I.,RAS Institute of Metal Physics
Journal of the Acoustical Society of America | Year: 2013

The interaction of conduction electrons with a longitudinal sound wave propagating in a crystal in a constant magnetic field is investigated. It is shown that the transverse spin current arises when the longitudinal sound wave propagation through the system. The average power absorbed by the spin subsystem of the conduction electrons and the spin-Hall conductivity have a resonant character. © 2013 Acoustical Society of America.

Mushnikov N.V.,RAS Institute of Metal Physics
Physics-Uspekhi | Year: 2012

The highest values of specific magnetic energy have been achieved in permanent magnets made of highly anisotropic intermetallide phases such as SmCo 5, Sm 2Co 17, and Nd 2Fe 14B. In tungsten- and gallium-doped Fe-Cr-Co alloys, by using hardening, annealing, and intense plastic rolling deformation, a multiphase nanocomposite state was formed instead of a conventional modulated structure, resulting in a high-strength high-plasticity material. Because the temperature change due to the demagnetization of a material is determined by magnetic entropy, it follows that compounds whose magnetization is strongly temperature-dependent near room temperature hold promise as magnetic cooling materials. The laboratory study of pressure and doping effects on the transition temperature, transition field, magnetic susceptibility, specific heat, and magnetostriction shows that the anomaly in physical properties associated with the small change in valence in a given compound is due to a fivefold increase in hybridization factor between f electrons and the conduction electrons.

Popov V.V.,RAS Institute of Metal Physics
Physics of Metals and Metallography | Year: 2012

Publications on the studies of interfaces in metals by the methods of Mössbauer (nuclear gammaresonance) spectroscopy are reviewed. Physical principles of the Mössbauer effect, various methods of nuclear gamma-resonance (NGR) spectroscopy and the Mössbauer spectra parameters are considered. The available results on grain boundary studies in coarse-grained and nanostructured materials and on interlayer interfaces in multilayers are analyzed. Capabilities of application of absorption and emission Mössbauer spectroscopy as well as of conversion electrons Mössbauer spectroscopy (CEMS) are discussed. © 2012 Pleiades Publishing, Ltd.

The cross-bridge working stroke is regarded as a continuous (without jumps) change of myosin head internal state under the action of a force exerted within the nucleotide-binding site. Involvement of a concept of continuous cross-bridge conformation enables discussion of the nature of the force propelling muscle, and the Coulomb repulsion of like-charged adenosine triphosphate (ATP) fragments ADP2- and Pi 2- can quite naturally be considered as the source of this force. Two entirely different types of working stroke termination are considered. Along with the fluctuation mechanism, which controls the working stroke duration tw at isometric contraction, another interrupt mechanism is initially taken into account. It is triggered when the lever arm shift amounts to the maximal value S ≈ 11 nm, the back door opens, and Pi crashes out. As a result, tw becomes inversely proportional to the velocity v of sliding filaments tw ≈ S/v for a wide range of values of v. Principal features of the experimentally observed dependences of force, efficiency, and rate of heat production on velocity and ATP concentration can then be reproduced by fitting a single parameter: the velocityindependent time span tr between the termination of the last and beginning of the next working stroke. v becomes the principal variable of the model, and the muscle force changes under external load are determined by variations in v rather than in the tension of filaments. The Boltzmann equation for an ensemble of cross-bridges is obtained, and some collective effects are discussed. © European Biophysical Societies' Association 2012.

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