Department of magnetism

Raman and Brillouin specroscopy group

Group structure:

  1. V.P. Gnezdilov, PhD, senior researcher, the head of group
  2. V.I. Fomin, PhD, senior researcher
  3. A.V. Peschnskii, PhD, senior researcher
  4. O.V. Afanasiev, engineer-researcher

The basic directions of researches:

  • Dynamics of a crystal lattice
  • Structural and magnetic phase transitions in multiferroics
  • Light scattering on spin waves in low-dimensional and frustrated magnetic structures
  • Lattice, charge, spin and orbital degrees of freedom determining the unique properties of metal-oxide compounds
  • Structural and electronic phase separation

Some important results:

  • Research of influence of incommensurable charge stripe-ordering on phonon and magnon spectra in low-dimensional nickelates;
  • Detection of interaction of structural and electronic phase separation in oxygen doped lanhtanum cuprate;
  • Detection of effect of huge phonon softening in doped manganites below metal-insulator transition temperature;
  • Detection of anomalous electronic Raman scattering in layered cobaltites NaxCoO2·yH2O;
  • Research of interraction between lattice and spin degrees of freedom in frustrated spin-chain compounds NaCu2O2 and α-TeVO4;
  • Detection of a fluctuating spin-state phase and a wipeout of the low-frequency phonon-scattering intensity under the influence of temperature and electromagnetic radiation in spin-crossover system [Fe(pmd)(H2O){Au(CN)2}2]·H2O.

Equipment:

  • Raman Jobin-Yvon U-1000 spectrometer;
  • Brillouin Burleigh RC-11 spectrometer;
  • Cryogenic equipment (2 - 300 K);
  • Magnetic field up to 3 T.



- Raman spectrometer.















Brillouin spectrometer.-




International co-operations:
Moscow State University, Moscow, Russia; Institute For Condensed Matter Physics, TU Braunschweig, Braunschweig, Germany; Chung-Ang University, Seoul, Korea; Institute of Applied Physics of the Moldavian Academy of Sciences, Kishinev, Moldova; Institute of Solid State Physics and Semiconductors of the Belarus Academy of Sciences, Minsk, Belarus; Institute for Microstructural Science Sciences National Research Council of Canada, Ottawa, Canada.

Recent publications:

  1. Yu.G. Pashkevich, V.A. Blinkin, V.P. Gnezdilov, V.V. Tsapenko, V.V. Eremenko, P. Lemmens, M. Fischer, M. Grove, G. Güntherodt, L. Degiorgi, P. Wachter, J.M. Tranquada, D.J. Butrey, Stripe conductivity in La1.775Sr0.225NiO4, Phys. Rev. Lett. 84, 3919 (2000).
  2. V.P. Gnezdilov, V.I. Fomin, V.S. Kurnosov, A.V. Peschanskii, V.V. Eremenko, H. Shmid, J.-P. Rivera, S. Gentil, Raman scattering in LiNiPO4 single crystal, ÔÍÒ 28, 288 (2002).
  3. V.P. Gnezdilov, A.V. Yeremenko, Yu.G. Pashkevich, P. Lemmens, G. Güntherodt, J.M. Tranquada, D.J. Buttrey, K. Nakajima, Electronic Raman scattering through the stripe ordering transition in La2-xSrxNiO4, ÔÍÒ 28, 716 (2002).
  4. P. Lemmens, V. Gnezdilov, N.N. Kovaleva, K.Y. Choi, H. Sakurai, E. Takayama-Muromachi, K. Takada, T. Sasaki, F.C. Chou, D.P. Chen, C.T. Lin and B. Keimer, Effect of Na content and hydration on the excitation spectrum of the cobaltite NaxCoO2·yH2O, Journ. Phys.: Cond. Mat. 16, S857 (2004).
  5. V.P. Gnezdilov, Yu.G. Pashkevich, J.M. Tranquada, P. Lemmens, G. Güntherodt, A.V. Yeremenko, S.N. Barilo, S.V. Shiryaev, L.A. Kurnevich, and P.M.Gehring, Interplay of structural and electronic phase separation in single crystallineLa2CuO4+0.05 studied by Neutron and Raman scattering, Phys. Rev. B 69, 174508 (2004).
  6. V.P. Gnezdilov, V. Kurnosov, Yu.G. Pashkevich, P. Lemmens, J.M. Tranquada, K.-Y. Choi, G. Güntherodt, K. Nakajima, A. Yeremenko, Phonons and magnons in stripe-ordered nickelates: A Raman scattering study, ÔÍÒ 31, 205 (2005).
  7. K.Y. Choi, P. Lemmens, G. Güntherodt, Yu. G. Pashkevich, V.P. Gnezdilov, P. Reutler, L. Pinsard-Gaudart, B. Büchner, A. Revcolevschi, Existence of orbital polarons in ferromagnetic insulating La1-xSrxMnO3 (0.11<x<0.14) revealed by giant phonon softening, Phys. Rev. B 71, 174402 (2005).
  8. K.Y. Choi, P. Lemmens, G. Güntherodt, Yu. G. Pashkevich, V.P. Gnezdilov, P. Reutler, L. Pinsard-Gaudart, B. Büchner, A. Revcolevschi, Orbiton-mediated multi-phonon scattering in La1-xSrxMnO3, Phys. Rev. B 72, 024301 (2005).
  9. K.Y. Choi, V. Gnezdilov, B.C. Watson, M.W. Meisel, D.R. Talham, P. Lemmens, Raman scattering measurements of the spin ladder compound (C5H12N)2CuBr4, Journ. of. Phys.: Cond. Matter 17, 4237 (2005).
  10. V. Gnezdilov, K.-Y. Choi, Yu. Pashkevich, P. lemmens, S. Shiryaev, G. Bychkov, S. Barilo, V. Fomin, A.V. Yeremenko, Low temperature mixed spin state of Co3+ in LaCoO3 evidenced from Jahn-Teller lattice distortions, ÔÍÒ 32, 219 (2006).
  11. K.-Y. Choi, V.P. Gnezdilov, P. Lemmens, L. Capogna, M.R. Johnson, M. Sofin, A. Maljuk, M. Jansen, B. Keimer, Magnetic excitations and phonons in spin-chain compound NaCu2O2, Phys. Rev. B 73, 094409 (2006).
  12. K.-Y. Choi, Yu.G. Pashkevich, V.P. Gnezdilov, G. Güntherodt, A.V. Yeremenko, D.A. Nabok, V.I. Kamenev, S.N. Barilo, S.V. Shiryaev, A.G.Soldatov, and P. Lemmens, Orbital fluctuating state in ferromagnetic insulating LaMnO3+δ studied using Raman spectroscopy, Phys. Rev. B 74, 064406 (2006).
  13. P. Lemmens, K.-Y. Choi, V. Gnezdilov, E.Ya. Sherman, D.P. Chen, C.T. Lin, F.C. Chou, B. Keimer, Anomalous electronic Raman scattering in NaxCoO2·yH2O, Phys. Rev. Lett. 96, 167204 (2006).
  14. R. Takagi, M. Johnsson, V. Gnezdilov, R.K. Kremer, W. Brenig, and P. Lemmens, Investigation of the novel oxohalogenide Cu4Te4O12Cl4 with Cu(II) tetrahedra, Phys. Rev. B 74, 04413 (2006).
  15. E. Meloshe, M.G. Cottam, V.P. Gnezdilov, D.J. Lockwood, One- and two-magnon Raman scattering in the canted antiferromagnet NiF2, JMMM 310, 1593 (2007).
  16. V. Gnezdilov, V. Bedarev, Yu. Pashkevich, P. Lemmens, S. Zvyagin, S. Gnatchenko, M. Pashenko, X. Mo, W. Queen, S.-J. Hwu, Structural phase transition in two-dimensional tetramer-cuprate Na5RbCu4(AsO4)Cl2, ÔÍÒ 33, 897 (2007).
  17. K.-Y. Choi, P. Lemmens, P. Scheib, V. Gnezdilov, Yu.G. Pashkevich, J. Hemberger, A. Loidl, V. Tsurkan, Anomalous electronic, phonon, and spin excitations in the chalcogenide spinel FeCr2S4, Journ. Phys.: Cond. Matter. 19, 145260 (2007).
  18. A. Donkov, M.M. Korshunov, I. Eremin, P. Lemmens, V. Gnezdilov, F.C. Chou, and C.T. Lin, Electron-phonon interaction in the laminar cobaltite NaxCoO2, Phys. Rev. B 77, 100504 (2008).
  19. V. Gnezdilov, P. Lemmens, A. A. Zvyagin, V. O. Cheranovskii, K. Lamonova, Yu. G. Pashkevich, R. K. Kremer, and H. Berger, Magnetic crossover and complex excitation spectrum of the ferromagnetic/antiferromagnetic spin-1/2 chain system α-TeVO4, Phys. Rev. B 78, 184407 (2008).
  20. A.V. Peschanskii, V.P. Gnezdilov, V.I. Fomin, V.V. Eremenko, P. Lemmens, K.-Y. Choi, H. Berger, Raman scattering study of a two-dimensional S=1 quantum spin system Ni5(TeO3)4Cl2, ÓÔÆ, ò. 54 ¹ 1-2, ñ. 205-211 (2009).
  21. V. Gnezdilov, P. Lemmens, P. Scheib, M. Ghosh, Yu. G. Pashkevich, H. Paulsen, V. Schünemann, J. A. Wolny, G. Agustí, and J. A. Real, Spectrum-sensitive phonon wipeout due to a fluctuating spin state in a Fe2+ coordination polymer, Phys. Rev. B 79, 045122 (2009).