Department of a Magnetic Properties of Solids

Head of the Department:Victor I.Val’kov,

doctor of physico-mathematical sciences,

(062) 311-00-45

Отдел Магнитных свойств Твердого Тела

Directions of Scientific Researches: Investigation of a solid magnetic properties under extreme conditions; determination of the conditions of the phase state stability in magnetics; establishment of the nature and transformation mechanisms between different magnetic states.

The investigation techniques: magnetometry in constant (up to 1.4 T) and pulse (up to 40 T) magnetic fields, X-ray and X-ray phase analysis, NMR- and NCR-spectroscopy of a high resolution, measurement of transport properties in a wide temperature range under high pressures.


Basic Results

For the first time there has been experimentally proved an existence of asperomagnetic structures in the magnetics with a competitive anisotropy, the structures having nuclear spin waves along with collective modes of electron-nuclear excitations with a regularly changing dispersion of magnetizations of the electron and nuclear subsystems at an invariable orientation of the average magnetic moments corresponding to them.

In the alloys on the base of iron and rhodium there has been revealed an effect of a ferromagnetic state suppression, iron atoms being substituted for nickel atoms at its further irreversible induction by a high pressure.

Using the methods of NMR and spin-spin relaxation, there has been studied a microscopic nature of a tremendous magnetoresistance in the perovskite-like manganites. In particular, there have been fixed the type of the charge carrier and the character of a magnetic phase transformation at the metal-dielectric transition; it has been shown that the ferromagnetic state has a complex two-phase structure, in a dielectric state an electric charge distribution density taking a wave character.

In the fluorine-silicate hexahydrates of bivalent metals there has been found a phenomenon of a barothermal freezing of high-entropy states. There have been determined peculiarities of the phase behavior and structure of the P-T-diagrams of these compounds (presence of special points, nonlinear boundaries of the phase stability areas, wide areas of meta-stable states, an exothermal character pf phase transformations etc.) connected with the phenomenon revealed.

There have been developed the models of phase transformations in magnetics based on the order parameter interaction. In the context of the models there is offered an explanation of the unique magneto structural behavior of some compounds of the 3-d metals. In particular, it has been demonstrated that an increase of the crystalline symmetry synchronous with a transition into a magneto-ordered state in the arsenides of the 3-d metals is conditioned by the concurrence of the order of magnetic and structural parameters; the order magnetic parameters presented by fluctuating exchange field have an essential influence on the formation of magnetic properties of electro-conducting crystals; in crystals with a triangle arrangement of magnetic ions the character of interaction of the order parameters specifies the type and conditions of the magnetic superstructure formation.

Applied researches

There has been developed the technology of a combined strengthening of mining and boring tools which includes plasma quenching of their working elements followed by magneto-pulse treatment. The technology guarantees favorable changes in the crystalline and dislocation structures of the elements mentioned and allows an increase of their operating life not less than by two times.

There has been developed the system of automatic temperature control in premises, devices, in technological processes, the system being based on the use of intellectual temperature-sensitive elements, digital converters, keys and other devices bound by a single double-wire line and digital exchange hardcopy log.

Selected publications

1. S.Zvyagin, H.Schwenk, B.Luthi, K.V.Kamenev, G.Balakrishnan, D.McK.Paul, V.I.Kamenev and Yu.G.Pashkevich. Ultrasonic and magnetic studies of Nd0.5Sr0.5MnO3. Physical Review B 62, 6104 (2000).

2. M.M.Savosta, P Novak. Two-Phase Character of Metallic Ferromagnetism in Manganites. Physical Review Letters 87, 137203 (2001).

3. M.M.Savosta, V.D Doroshev, V.A.Borodin, Yu.G.Pashkevich, V.I.Kamenev, T.N.Tarasenko, J.Englich, J.Kohout, A.G.Soldatov, S.N.Barilo, S. V.Shizyaev. Nuclear quadrupole resonance of barium in BaBiO3 and BaPbO3. Physical Review B 63, 184106 (2001).

4. K.V.Kamenev, S.K.Asadov, V.I.Kamenev, I.S.Maksimov, B.M.Todris. Phase transitions in the Mn-Zn fluorosilicate hexahydrates. Journal of Physics: Condensed Matter 13, 3709 (2001).

5. Yu.D.Zavorotnev, L.I.Medvedyeva. Longperiod incommensurate structures in crystals with a triangular arrangement of magnetic ions. Journal of Magnetism and Magnetic Materials 248, 402 (2002).

Scientific composition of department

Зав.отделом,    ВАЛЬКОВ Виктор Иванович
доктор физико-математических наук, старший научный сотрудник    (062) 311-00-45