Department of Physics of Phase Transformation
Head of the Department: Georgi G.Levchenko,
doctor of physico-mathematical sciences
Directions of Scientific Researches: Electron states and their developments in magnetic, optical and electroconductive properties at phase transformations: in metal-organic compounds with a changing spin state; in molecular and molecular-like compounds possessing a long magnetic order; in HTSC-compounds and compounds possessing a tremendous magneto resistance.
The investigation techniques: X-ray analysis; magnetometry in a wide range of temperatures, pressures, magnetic fields; EPR; optical and Mossbauer spectroscopy; chemical substitution.
A pressure-induced full low spin-high spin transformation was first detected in iron-bearing metallic-organic comounds. For the first time a spin volume was experimentally detected in the quantum system îÅ3.
It was found out that a structural dimensionality of metallic-organic compounds is of a crucial importance in the behavior of the phase high spin-low spin transformation in ironbearing compounds. This importance is conditioned by the character of intra- and interchain interactions which are determined by the availability of hydrate or π-π-bonds.
In some organic and non-organic substances there were revealed and studied magnetic centers marked by the appearance of a non-centrality effect. An important peculiarity of the centers revealed is the fact that they were formed by ions of trivalent iron Fe3+. We can conclude that the non-centrality effect is characteristic of Fe3+ ions in organic and non-organic substances of different composition and structure.
It was established that vibrone and mixed states play an essential role in the formation of temperature-dependent characteristics of some metallic-organic and perovskite systems, namely, the character of conductivity, EPR-spectrum, magneto resistive effect etc.
There have been determined the ways of current flow in the vicinity of ôĶ , and the superconductivity dimensionality in HTSC-films of different thickness.
1. Y.Garsia, V.Ksenofontov, G.G.Levchenko, P.Gutlich. Pressure effect on novel spin transition polymeric chain compound. Journ. Mater. Chemistry 10, 2274 (2000).
2. G.G.Levchenko, A.Caneschi, A.Dei, F.Fabrizi. Pressure and ôemperature Inducted Valence Tautometric Interconversion in o-Dioxolene Adduct of a Cobalt Tetraaramacrocycle Complecses. Chem.Eur.J. 7, 3926 (2001).
3. V.Ksenofontov, G.G.Levchenko, S.Reiman, P.Guetlich, A.Bleuzen, V.Escax, M.Verdaguer. Pressureinduced electron transfer in ferromagnetic Prussian blue analogs. PHYSICAL REVIEV, B 68, 024415, (2003).
4. V.N.Vasyukov, V.V.Shapovalov, S.A.Schwarz, M.H.Rafailovich, J.C.Sokolov, V.A.Shapovalov. Temperature induced changes in the EPR spectrum of the magnetic center in kaoline. J.Magn.Resonance. 154, 15 (2002)
5. V.A.Voloshin, A.Gusev, I.A.Danilenko, L.I.Medvedeva, A.D.Prokhorov, S.I.Khartsev. Interplay of structure, magnetism and resistivity of La0.5Ca0.54MnO3+x Physics Letters A 271, 121, (2000).
6. V.A.Khokhlov, A.Yu.Prokhorov, V.F.Drobotko, G.G.Levchenko, A.V.Klimov. Manifestation of two-dimensional behavior of YBCO-films when studying their complex susceptibility. FNT6 (28), 535 (2002).