Персона: Савченков, Павел Сергеевич
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Институт лазерных и плазменных технологий
Стратегическая цель Института ЛаПлаз – стать ведущей научной школой и ядром развития инноваций по лазерным, плазменным, радиационным и ускорительным технологиям, с уникальными образовательными программами, востребованными на российском и мировом рынке образовательных услуг.
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- ПубликацияТолько метаданныеDramatic impact of intermediate-valence impurity on induced magnetism in singlet ground state system PrNi(2020) Clementyev, E. S.; Lazukov, V. N.; Savchenkov, P. S.; Alekseev, P. A.; Савченков, Павел Сергеевич; Алексеев, Павел Александрович© 2020 Elsevier B.V.We studied the influence of La (nonmagnetic) and Ce (intermediate valence) impurities on the ferromagnetic ordering temperature Tc of compounds RE1-x(La,Ce)xNi (RE = Pr, Gd). The ordering temperature Tc was measured in a wide range of impurity concentration. Crystal electric field (CEF) splitting for the PrNi and Pr0.25Ce0.75Ni was defined by neutron spectroscopy measurements. The strong difference in the influence of La and Ce on Tc of PrNi and GdNi based systems has been obtained. The introduction of a spin-fluctuating intermediate valence impurity in PrNi leads to a dramatic increase in the area of the ordered state on the phase diagram, due to an increase in Tc, compared to the impact of La-impurity over the entire concentration range. The dependence of Tc on the Ce concentration for the Pr1-xCexNi was calculated within the framework of the model of microscopic states. The essential modification of the CEF splitting by the Ce impurity appears to be the decisive factor affecting Tc wherein the Ce ion carries zero static magnetic moments similar to the La case. The latter explains the identical dependencies of the ordering temperature on the impurity concentration observed in systems with a long-range order of local magnetic moments Gd1-xLaxNi and Gd1-xCexNi.
- ПубликацияТолько метаданныеInduced magnetism and “magnetic hole” in singlet ground state system PrNi(2019) Clementyev, E. S.; Lazukov, V. N.; Savchenkov, P. S.; Alekseev, P. A.; Савченков, Павел Сергеевич; Алексеев, Павел Александрович© 2019 Elsevier B.V.The phenomenon of “induced magnetic ordering” for the local magnetic moments with singlet ground state in a periodical lattice is considered for the prototype intermetallic rare-earth compound PrNi ordered ferromagnetically at temperature TC = 21 K. Within the framework of a realistic model the energy dispersion relations are obtained for the magnetic excitations above Tc along the high symmetry directions. The “soft mode” behaviour observed for the acoustic magnetic excitation along (q 0 0) direction is reproduced. The influence of the substitution of isovalent nonmagnetic La for Pr1−xLaxNi on the temperature of ferromagnetic ordering is investigated. The linear decrease of the ordering temperature TC down to zero value in increasing of the La concentration up to x = 0.5 is observed and described by the model.
- ПубликацияОткрытый доступUncommon Magnetism in Rare-Earth Intermetallic Compounds with Strong Electronic Correlations(2023) Savchenkov, P. S.; Alekseev, P. A.; Савченков, Павел Сергеевич; Алексеев, Павел АлександровичRare-earth intermetallic compounds are characterised by the presence of a long-range magnetic order due to the interaction of local magnetic moments periodically located within the crystal lattice. This paper considers the possibility of forming an ordered state in cases where there is no opportunity to observe the local moment of the f-electronic shell in a traditional sense. These are, first of all, systems with a singlet ground state, as well as systems with fast spin fluctuations caused by a homogeneous intermediate-valence state of a rare-earth ion. Extensive experimental studies of these effects using neutron diffraction, neutron spectroscopy, and high-pressure studies of the magnetic phase diagram are presented and analysed, and the corresponding microscopic model representations are discussed. In particular, the possible origin of long-range magnetic order in mixed-valence compounds is analysed.
- ПубликацияОткрытый доступSpectral characteristics of the antiferromagnetic spin-1/2 Heisenberg model on the square lattice in a magnetic field(2021) Barabanov, A. F.; Savchenkov, P. S.; Савченков, Павел Сергеевич© 2020 Elsevier B.V.We predict that spin-waves in an ordered square quantum antiferromagnet in a magnetic field (h) perpendicular to antiferromagnetic plane may demonstrate three modes of spin excitations. Starting from the self-consistent rotation-invariant Green's function method, a new mean-field theory is constructed for h≠0. The method preserves the translational and the axial symmetries, and provides exact fulfillment of the single-site constraint for each of the three modes. We examine the dynamical structure factors Sαα(k,ω),α(β) = x, y, z. It is shown, that the introduction of h leads to the hybridization of two degenerate spin modes due to the appearance of a nondiagonal on α,β spin-spin Green's functions. The comparison of the theory with the exact diagonalization study and with results on inelastic neutron scattering experiments is discussed at T = 0. We discuss also the correspondence of the present theory to the existing theories, which allow only two spin excitations modes for the total S(k,ω).