Papers by Author: V. M. Cherepanov

Abstract: sup>119Sn Mössbauer spectroscopy was used to study the transition from single-ion Kondo behavior in the magnetically ordered state in the heavy-fermion intermetallic СePdSn. Found that the temperature evolution of the experimental spectra agrees with the calculations within the two-level relaxation model. This allows one to treat magnetic structure of CePdSn as the decomposition of the total volume of the СePdSn sample into the antiferromagnetic domains. The temperature dependence of the frequency of fluctuations of the domains magnetization and the distribution density of itinerant electrons near the tin atoms in the process of RKKY interaction are investigated.

Abstract: A process of the biodegradation in vivo of a magnetic ferrofluid was investigated by Mössbauer spectroscopy. After the injection of the ferrofluid in a mice body an additional doublet was observed in the Mössbauer spectra of the mice liver. Further analysis showed that the doublet consists of two components with different magnetic properties. The components related both to the formation of non-magnetic ferritin-like proteins and superparamagnetic behavior of the injected nanoparticles. These components were separated in an external magnetic field and the time evolution of each fraction was studied. The concentration of both of these fractions in the frame of multi-level relaxation model was estimated.

Abstract: Film composites based on magnetite Fe₃O₄ nanoparticles in the polyvinyl alcohol (PVA) matrix and the dried ferrofluid ARA-250 (Chemicell GmbH, Germany) were studied at temperatures 78-300 K by Mössbauer spectroscopy and magnetic measurements in magnetic fields H < 5 kOe. The Mössbauer spectra taken in magnetic fields show essential restoration of the magnetic hyperfine structure characteristic for the nanoparticles. The experimental Mössbauer spectra have been analyzed within the recently developed three-level [ and multi-level [ relaxation models of magnetic dynamics in an ensemble of single-domain particles. These models take into account the precession and diffusion of particles uniform magnetization as well as the particles size distribution and interparticle interactions.

Abstract: The mixed perovskites (Bi1-xSrx)FeO3-y (x = 0.07, 0.14, 0.25 and 0.50) were studied by 57Fe Mössbauer spectroscopy in the temperature range 87–700 K. The samples were prepared by conventional ceramic technology with 10% 57Fe isotope enrichment. X–ray diffraction measurements showed that the samples were single-phase and had a rhombohedral structure at x = 0.07 and a cubic one at x = 0.14-0.50. As the strontium content x increases, the Neel temperature TN(x) increases from 640 K (x = 0) to 670 K (x = 0.25) and then decreases to 637 K (x = 0.5). The similar dependence on x was found for the hyperfine field values B(x) at T = 87 K. The experimental Mössbauer spectra are satisfactorily described by three to four Fe3+ states with the room temperature isomer shift values in the range 0.17-0.43 mm/s, which correspond to the iron sites with 4, 5 and 6 oxygen neighbours.