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>> Românã

Serban, Gr. Constantin Constantinescu

National Institute for Material Physics, Bucharest, Romania

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Born: 1945

Interests: solid state, mineralogy, dimension and dimensionality effects in magnetic materials, efect Mössbauer(NGR)

Theoretical aspects of the Mössbauer's line shape in the coupled (electric and magnetic)hyperfine interactions:
a) polarized gamma-ray transition probabilities;
b) Mossbauer scattering probability;
c) Blume's stochastic solution of the Mössbauer line shape.

"Magnetic phase transition in compounds with cupled magneto-electric properties."
- Experimental studies on boracite compounds NixFe3-xB7O13 x=0 ÷ 0.6 investigated by Mossbauer spectroscopy, IR spectroscopy; from He-temperature to 600K; magnetic and structural phase transition, displacements of Fe+2, I-1 ions and antiferromagnetic, weak-ferromagnetic orientation problems; some methodological problems of Mossbauer 57Fe spectra.
- Computer programs:
a) simulation and fitting programs for Mossbauer (transmition) spectra for powder and monocrystalline sample with usual and polarized gama ray;
b) to calculate the hyperfine magnetic fields at 57Fe in the boracites.

"Structure and phase transitions studied by resonance experimental technics in ordered and disorder materials."
- The teoretical aspects and experimental investigations of ferroelectric phase transition on (NH4)2SO4:57Fe, Cd+,Hg+; ESR, Mössbauer resonance; low temperature measurements; ferroelectric phase transition; temperature dependence of Debaye- Waller factor.
- Theoretical aspectes and experimental investigations of cation substitution and magnetic phase transition on ferrigehlenites A(Ba,Sr)2Fe2B(Ge,Si)O7 and on synthetic Ba,Sr(La,Nd)-iron-germanates:A3Fe2Ge4O14 and RA2Fe3Ge3O14 (A=Ba,Sr;R=La,Nd); cation-substitution in Thompson cubes and tetrahedral, octahedral positions by +3 ions inequivalence, crystalline chemistry and magnetic ordering problems;room to hellium temperature Mossbauer measurements, dispersion of the electric field gradient values at Mössbauer isotope sites in Ca-gallogermanites structures.
- The distribution of crystalline fields in static disordered media.
- The structural aspects and experimental investigations on minerals (silicates: olivines, ampyboles, etc.), ferrites, etc. crystalline chemistry, temperature and pressure genesis conditions of some geological romanian deposits; role of neighborhood distortion of cation sites; room and low temperature Mossbauer measurements.
- Theoretical aspects of applied Group Theory and Molecular Orbital Theory in the phase transitions.
- Computer programs:
a) to calculate the temperature dependence of Mossbauer-factor in the ferroelectric and paraelectric region (taking into account the soft-mode;
b) to calculate the lattice and ionic electric field gradient in the approximation of point-electric charges and dipoles and respectively in the frame of Molecular Orbital Theory;
c)electic and magnetic hyperfine fields' distribution in static disordered crystalline media


Selected publications:
• L. DUTA, G. DORCIOMAN, A. C. POPESCU, I. N. MIHAILESCU, P. NITA, I. MERCIONIU, A. BIRSAN, I. BIBICU, S. CONSTANTINESCU, N. POPESCU-POGRION. Structural investigations on electrodes - electrolytes systems for intermediate temperature solid oxide fuel cell applications. OPTOELECTRONICS AND ADVANCED MATERIALS - RAPID COMMUNICATIONS, vol. 6, 11-12, pp. 1073-1080, 2012.
• Maria Nicoleta Grecu, Serban Constantinescu, Doina Tarabasanu-Mihaila, Daniela Ghica, and Ion Bibicu. Spin dynamics in 57Fe-doped TiO2 anatase nanoparticles. Phys. Status Solidi B 248, 12, p. 2927–, 2011.
• Turcu F, Simon S, Constantinescu S., Grecu N., Iuga D. " Stuctural changes of pezoelectric La3Ga5SiO14 induced by paramagnetic ions revealed by 71Ga multiple quantum magic angle spinning" . Sol. Stat. Mag. Res. , 36, pp. 92-95, 2009.
• V. V. Grecu, S. Constantinescu, Maria Nicoleta Grecu, Rodica Olar, Mihaela Badea and Rodica Turcu. Magnetic characterization of some nanometric i. Hyperfine Interactions, 183, pp. 205-214, 2008.
• S. Constantinescu, L. Diamandescu, I. Bibicu, D. Tarabasanu-Mihaila, M. Feder, . Hyperfine interactions and dynamics characteristics of 119Sn in xSnO2-(1-x)a-Fe2O3 nanoparticle system. Hyperfine Interactions, 184, pp. 83-89 , 2008.
• S. Constantinescu, I. Mercioniu, N. Popescu-Pogrion . Mathematical model for uniform huge grains growth. Journal of Optoelectronic and Advanced Materials, 10 (11), pp. 3083-3085, 2008.
• S. Georgescu, S. Constantinescu, A. M. Chinie, A. S. Stefan, O. Toma, I. Bibi. Optical and Mossbauer studies on YAG:Eu nanocrystals synthesized. In SPIE Proceedings , 6785, pp. 67850A01-6. 2007.
• B. S. Vasile, Cristina Ghitulica, Nicoleta Popescu-Pogrion, S. Constantinescu , Ionel Mercinoiu, Raluca Stan, Ecaterina Andronescu. Structural Investigations on Yttria - Doped Zirconia Nanopowders Obtained by Sol-Gel Method. Journal of Optoelectronic and Advanced Materials , 9 (12), pp. 3774-3780, 2007.
• E. Burzo, I., Balasz, S. Constantinescu, I. G. Deac. Grain boundary effect in highly ordered Sr2FeMoO6. Journal of Magnetism and Magnetic Materials, 316, pp. 741-744, 2007.
• S. Constantinescu. Distribution of electric and magnetic hyperfine fields in Fe-rich gallo-germanates. Hyperfine Interactions, 168, pp. 1121-1125, 2006.
• M. Raekers1, *, K. Kuepper1, #, H. Hesse1, I. Balasz2, I. G. Deac2, S. Constantinescu3 , E. Burzo2, . Investigation of chemical and grain boundary effects in highly ordered Sr2FeMoO6: XPS Mössbauer studies. Journal of Optoelectronics and Advanced Materials (ISSN 1454-4164), 8, pp. 455-460, 2006.
• E. D. Ion, S. Constantinescu, M. Bunescu, R. Ramer. Eu-Doped _PtT ceramics. I Preparation and structural investigation. Ferroelectrics, 294, pp. 85-92, 2003.
• L. Gheorghe, S. Georgescu, S. Constantinescu, I. Mateescu, L. Diamandescu, L. Dumitrache and E. Borca. Synthesis, growth and characterisation of langasit crystals. In ISBN: 0-7803-7583-1 (ed.), Proceeding of 2002 IEEE International Ultrasonics Ferroelectrics and frequency Control Society, Munich, Germany, pp. 940-943. 2002.
• M. N. Grecu, S. Constantinescu, V. V. Grecu. Lattice dynamics in ammonium sulphate: EPR and Mössbauer results. Proceeding of 30th AMPER 2000 on Magnetic Resonance and Related Phenomena, VI, Lisbon, Portugal, pp. 449-453, 2001.
• S. Constantinescu - D. Tarina. Crystal-chemistry aspects and electric-field-gradient (EFG) dispersion in Ca-gallogermanate-type structures studied by Mössbauer spectroscopy. European Physical Journal B, 13, pp. 75-81, 2000.
• S. Constantinescu - M. N. Grecu. The Mössbauer and magnetic resonances investigations of structural phase transitions in K2ZnCl4crystals. Eur. Phys. J. B, 13, pp. 227-233, 2000.
• S. Constantinescu , Gh. Udubasa and S. Calogero. 57Fe Mössbauer Spectroscopy on Two Romanian Carpathian Pumpellyites. Journale de Physique I France, 7, p. 777_784, 1997.
• D. Barb, S. Constantinescu and D. Tarina. Electric Field Gradients at 57Fe Nuclei in the Sr3Fe2Ge4O14 Trigonal Germanate. Journale de Physique I France, 7, p. 1701_1708, 1997.
• D. Barb, S. Constantinescu and D. Tarina. 57Fe Mössbauer Spectroscopy on Disordered Crystalline Media with Ca-Gallogermanate Type Structure, II Below the Magnetic Ordering Temperature. Hyperfine Interactions, 96, pp. 83-89, 1995.
• D. Barb, S. Constantinescu and D. Tarina. 57Fe Mossbauer Spectroscopy on Disordered Crystalline Media with Ca-Gallogermanate Type Structure, I In Paramagnetic Region. Hyperfine Interactions, 96, pp. 73-82, 1995.
• D. Barb, S. Constantinescu, S. Nistor, D. Tarina. Mossbauer Spectroscopy on 57Fe:NaCl crystals. Hyperfine Interactions, 53, pp. 279-284, 1990.
• D. Barb, S. Constantinescu, D. Tarina, I. S. Lyubutin, B. V. Mill, V. G. Terziev, T. D. Dmitrieva and A. V. Butashin. Magnetic hyperfine fields in ferrigehlenttes. Hyperfine Interactions, 50, pp. 645-650, 1989.


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