I. P. Aleksandrova

Publications (5)4.08 Total impact

• Article: Measurement of the maximum content of bound water in bentonitic clay using dielectric and NMR methods

  V. L. Mironov, A. A. Sukhovskii, Yu. I. Lukin, I. P. Aleksandrova
  [show abstract] [hide abstract]
  ABSTRACT: An investigation of moisture dependences of refractive index and spectral width of the nuclear magnetic resonance (NMR) is performed for bentonitic clay specimens at different temperatures. These moisture dependences allowed identifying two types of moisture: bound and free water. The maximum content of water in the bentonitic clay is measured. Keywordsdielectric permittivity–nuclear magnetic resonance–bentonitic clay–bound water
  Russian Physics Journal 04/2012; 54(1):71-76. · 0.41 Impact Factor
• Article: Effect of impurities on the successive phase transitions in (Cs1−xRbx)2ZnI4 compounds

  I P Aleksandrova, J Bartolomé, L R Falvello, J M Torres, A A Sukhovskii
  [show abstract] [hide abstract]
  ABSTRACT: The heat capacity, nuclear quadrupole resonance (NQR) and x-ray diffraction of (Cs1−xRbx)2ZnI4 single crystals have been measured, for x = 0, 0.001, 0.005, 0.01, 0.025 and 0.05. The normal to incommensurate (N–Inc) phase transition at TI, the incommensurate to commensurate (Inc–C) lock-in transition at TL and the structural commensurate monoclinic to triclinic transition at TLT, observed in the parent compound (x = 0), takes place for x = 0, 0.001, 0.005 and 0.01. For x = 0.025 only TI and TL are detected, while for x = 0.05 no transitions were observable. The values of TI and TL increase with x while TLT decreases and disappears at the concentration x = 0.025. The effect of defects, besides modifying the transition temperatures, is that of broadening and lowering the heat capacity anomaly at the lock-in transition until its total quenching for x = 0.05. No observable hysteresis is detected in this transition. NQR and x-ray diffraction data show the Inc–C transition up to the highest concentration. We conclude that this phenomenology is caused by weak interaction of the incommensurate modulation with point defects even in the region close to the Inc–C transition.
  Journal of Physics Condensed Matter 11/2002; 14(49):13623. · 2.55 Impact Factor
• Article: Phase Transitions of Cs3Sb2I9 , Cs3Bi2I9  , and Cs3Bi2Br9 Crystals

  Yu. N. Ivanov, A. A. Sukhovskii, V. V. Lisin, I. P. Aleksandrova
  [show abstract] [hide abstract]
  ABSTRACT: The phase transitions of Cs3Sb2I9, Cs3Bi2I9, and Cs3Bi2Br9crystals were investigated by 133Cs nuclear magnetic resonance. Cs3Bi2Br9was also studied by 87Br nuclear quadrupole resonance. The parameters of the Cs electric-field gradient tensors were determined. The phase transitions were shown to produce significant changes in the nearest neighbor environment of only one of two inequivalent Cs sites. In Cs3Sb2I9, the tensors remain axisymmetric below the transition at 85 K, in line with the assumption relying on powder x-ray diffraction data that, below the transition temperature, Cs3Sb2I9has a trigonal structure. The observed temperature variation in the shape of the 133Cs NMR and 127I NQR signals suggests that Cs3Bi2I9may undergo a transition to an incommensurate phase.
  Inorganic Materials 05/2001; 37(6):623-627. · 0.41 Impact Factor
• Article: NMR lineshape and phase soliton effects in incommensurate Rb2ZnCl4

  R Blinc, I P Aleksandrova, A S Chaves, F Milia, V Rutar, J Seliger, B Topic, S Zumer
  [show abstract] [hide abstract]
  ABSTRACT: In incommensurate systems the NMR, NQR or EPR resonance frequency varies in space in a way which reflects the spatial variation of the incommensurate modulation wave. An evaluation of the magnetic resonance lineshape for the case of a multi-soliton lattice is presented for different ratios between the soliton width and the inter-soliton spacing as well as for different relations between the resonance frequency and the incommensurate order parameter. The results are compared with the experimental data in Rb2ZnCl4. It is found that in this system the soliton width is large compared with the inter-soliton spacing over most of the incommensurate phase. The temperature variation of the phase soliton density has been determined. The non-classical value of the critical exponent beta =0.35+or-0.03 for the amplitude of the order parameter demonstrates that the whole incommensurate phase is critical in this one-dimensionally modulated system.
  Journal of Physics C Solid State Physics 11/2000; 15(3):547.
• Article: Structural phase transitions in the Cs3Sb2I9 crystal

  I. P. Aleksandrova, A. A. Sukhovskii, S. V. Mel’nikova, L. I. Shabanova, A. I. Zaitsev, J. J. Melero, J. Bartolomé
  [show abstract] [hide abstract]
  ABSTRACT: A sequence of two phase transitions at 85.3±0.6 K and 72.6±0.4 K is observed in hexagonal Cs3Sb2I9. The NQR spectra of 127I are analyzed, optical polarization studies are made, and the thermal properties, linear expansion coefficients, and stiffness constants are measured over a broad range of temperatures below room temperature.
  Physics of the Solid State 04/1997; 39(5):846-848. · 0.71 Impact Factor