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1.
E. V. Nefeodova N. N. Tiden K. Siemensmeyer P. A. Alekseev V. N. Lazukov I. P. Sadikov N. Yu. Shitsevalova 《Journal of Experimental and Theoretical Physics》2007,105(1):12-13
The roles of various physical mechanisms in the properties of the ground state of the Pr ion in PrB6 are studied by measuring magnetic excitation spectra in the paramagnetic and magnetically ordered phases of polycrystalline PrB6. The ground state of the Pr ion in the paramagnetic phase is experimentally found to be triplet Γ5. During the transition into the magnetically ordered state, this triplet splits into three singlet levels. The results obtained do not exclude the appearance of an additional contribution to the splitting induced by a decrease in the local symmetry because of structural distortions. 相似文献
2.
V. N. Lazukov P. A. Alekseev E. S. Klement’ev E. V. Nefedova I. P. Sadikov J. -M. Mignot N. B. Kol’chugina O. D. Chistyakov 《Journal of Experimental and Theoretical Physics》1998,86(5):943-952
To examine the effect of hybridization of 4f electrons with conduction electrons on the crystal field potential using neutron spectroscopy, we studied the effects of
the crystal electric field (CEF) in intermetallic compounds of the type ReNi, in which chemical substitution is followed by
a transition of the cerium ions from an intermediate valence state to the Kondo state. Measurements were performed both on
cerium ions in the compounds Ce1−x
LaxNi (x=0.5, 0.8), where they have a whole-number population of the 4f shell, and on the paramagnetic impurity ion Nd in the series of compounds Re1−x
NdxNi (Re=Ce, La, Y), in which the cerium ions are found either in an intermediate valence state or in the Kondo state. From
the neutron inelastic magnetic scattering spectra on Nd ions, we have reconstructed the crystal field parameters in ReNi compounds
and calculated the CEF level diagram of Ce ions in these compounds as functions of the interion distances Re-Ni. The results
of our calculations are in good agreement with the experimentally determined splitting diagram of the ground-state multiplet
of the Ce ions. We have determined that as the degree of hybridization with the conduction electrons grows the CEF potential
varies considerably and the effective splitting of the 4f shell of the cerium ions increases. The estimated energy scale of the splitting of the ground-state multiplet of the Ce3+ ions in the ReNi CEF (ΔCEF∼15 meV) turns out to be commensurate with the Kondo temperature (T
K
;140 K for CeNi. Analysis indicates that the CEF potential has a substantial effect on the formation of the valence-unstable
ground state of the f shell in this compound.
Zh. éksp. Teor. Fiz. 113, 1731–1747 (May 1998) 相似文献
3.
P. A. Alekseev V. N. Lazukov K. S. Nemkovskii I. P. Sadikov 《Journal of Experimental and Theoretical Physics》2010,111(2):285-291
The neutron inelastic scattering data for the spectra of f-electron excitations in valence-unstable semiconductors SmB6, SmS, and YbB12 are discussed. The conclusions on the relation of the spectral characteristics to the nature of exciton-type states formed
in these systems are reported. 相似文献
4.
P. A. Alekseev E. S. Klement’ev I. V. Kovalev V. N. Lazukov A. V. Rybina I. P. Sadikov A. P. Menushenkov R. V. Chernikov V. V. Sidorov O. V. Grishina 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(5):622-624
Heat capacity measurements of amorphous and crystallized R16.7Ni83.3 (RNi5) samples (RNi5) (R = La, Pr) in magnetic fields were performed, along with measurements of the average interatomic Ni–Ni distances and average
square deviations from the interatomic distances. Changes were observed in the interatomic distances in La16.7Ni83.3, and in the electron component of the Pr16.7Ni83.3 heat capacity. 相似文献
5.
Alekseev PA Mignot JM Nemkovski KS Rybina AV Lazukov VN Ivanov AS Iga F Takabatake T 《J Phys Condens Matter》2012,24(20):205601
Peculiarities in the lattice dynamics of the Kondo insulator Y bB(12) have been studied by inelastic neutron scattering. Selected phonon modes were traced above and below the temperature region (T ~ 50 K) where the gap opens in the electron density of states. The intensities of some low-energy modes exhibit an anomalous temperature dependence for q vectors close to the Brillouin zone boundary, suggesting a renormalization of the phonon eigenvectors. This effect is thought to arise from a coupling with magnetic excitations of the same symmetry, which exist at nearby energies. It is argued that this magnetovibrational coupling may in turn play a role in the steep temperature crossover existing in Y bB(12) between the low-temperature (Kondo insulator) and high-temperature (incoherent spin-fluctuation) regimes, which is rapidly suppressed by lighter Zr substitution. 相似文献
6.
E. S. Clementyev P. A. Alekseev V. V. Efimov I. O. Troyanchuk A. S. Ivanov V. N. Lazukov V. V. Sikolenko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(4):553-558
The energy structure and temperature evolution of the magnetic excitation spectra of Pr0.5Sr0.5CoO3 are studied by inelastic neutron scattering. The measurements are performed on a polycrystalline sample of Pr0.5Sr0.5CoO3 and its non-magnetic analogue La0.5Sr0.5CoO3 on the high intensity time-of-flight spectrometer IN4 (ILL, Grenoble) in the temperature range 10 K < T < 300 K. The crystal electric field parameters in Pr0.5Sr0.5CoO3 are calculated and the splitting scheme of the 4f ground multiplet of Pr3+ ions is determined based on the experimental data. 相似文献
7.
Alekseev P. A. Znamenski N. V. Lazukov V. N. Kelin V. E. Kovalev I. A. Kruglov S. L. Nefedova E. V. Sadikov I. P. 《Crystallography Reports》2006,51(1):S79-S84
The presence of an unfilled f-electron shell in rare earth intermetallic compounds under conditions of strong electron correlation between localized and delocalized electrons is responsible for the formation of local magnetic moments. According to the data of neutron, synchrotron, and other investigations of a number of such systems, the interaction of these moments with the local crystalline environment, hybridization with conduction electrons, f-f correlations (i.e., both one-site and cooperative phenomena), and combinations of these main effects form the physical base for the reconstruction of the excitation spectrum of an f-electron system and appearance of pronounced specific features of thermodynamic characteristics. The range of characteristic temperatures of these anomalies is determined by the interaction energy, which generally corresponds to the range 1–100 K. For some intermetallic compounds, the additional component of the specific heat (of electron origin) may greatly (by two to three orders of magnitude) exceed the specific heat of conventional structural materials. This feature makes it possible to consider such systems as promising functional materials (a kind of thermodynamic dampers) capable of compensating for various thermal perturbations in low-temperature super-conducting magnetic systems. 相似文献
8.
P. A. Alekseev J. -M. Mignot E. V. Nefedova K. S. Nemkovskii V. N. Lazukov I. P. Sadikov A. Ochiai 《JETP Letters》2004,79(2):81-84
The dynamic magnetic susceptibility spectrum in a single-crystal sample of the intermediate-valence compound Sm0.67Y0.33S is studied by inelastic neutron scattering with neutron momentum transfer and sample temperatures varying over wide ranges. Two coupled collective modes have been found in the spectrum. Unlike the higher energy mode, whose intensity approximately follows the form factor of Sm2+, the lower energy mode exhibits a stronger angular dependence than could be expected from the form factor for the localized f electrons. The total intensity of the inelastic component of the magnetic response decreases with increasing temperature; this is accompanied by the appearance of a broad quasi-elastic signal of a magnetic nature at significantly lower temperatures than follows from the calculated intensities of the transitions within the excited multiplet of the Sm2+ ion. An analysis of the observed features allows the suggestion to be made that the fine structure of the magnetic excitation spectrum in (Sm,Y)S is associated with the formation of an exciton-like intermediate-valence state on Sm ions rather than with the crystal-electric-field effects. 相似文献
9.
P. A. Alekseev V. N. Lazukov N. N. Tiden R. Kahn J. -M. Mignot A. Podlesnyak E. S. Clementyev I. P. Sadikov 《Crystallography Reports》2007,52(3):398-402
The inelastic neutron scattering spectra of the CeAl3 heavy-fermion system are measured over a wide range of momentum transfers with the aim of determining the type of ion-ion magnetic correlations. The oscillatory dependence of the intensity of quasi-elastic magnetic neutron scattering on the momentum transfer is revealed at temperatures lower than those corresponding to the energy of splitting in the crystal electric field. An analysis of the obtained dependence of the intensity of quasi-elastic magnetic neutron scattering indicates the presence of short-range ferromagnetic correlations in the system. 相似文献
10.
P. A. Alekseev V. N. Lazukov 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(8):1057-1058
The peculiarities of the transition of LaNi5 films from the metastable amorphous state to the equilibrium crystalline state have been studied. It is shown that surface coatings with a composition corresponding to LaNi5 can be obtained, which have, depending on the deposition and treatment conditions, structures from amorphous to single-phase crystalline, free of internal stress. 相似文献