Персона: Алексеев, Павел Александрович
Загружается...
Email Address
Birth Date
Научные группы
Организационные подразделения
Организационная единица
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.
Статус
Фамилия
Алексеев
Имя
Павел Александрович
Имя
4 results
Результаты поиска
Теперь показываю 1 - 4 из 4
- 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.
- ПубликацияТолько метаданныеBinary and Pseudobinary Invar Materials based on Intermediate Valence Compounds(2019) Serebrennikov, D. A.; Clementyev, E. S.; Alekseev, P. A.; Алексеев, Павел Александрович© 2019, Pleiades Publishing, Ltd.Abstract—: A new type of binary and pseudobinary invar materials based on intermediate valence samarium compounds Sm0.8B6, Sm1 – xLaxB6 (x = 0, 0.1, 0.22, and 0.5), Sm0.67Y0.33S, Sm0.55Y0.45S, and Sm2.75C60 are developed. The Weiss two-level invar model is used to describe the anomalous contribution to the coefficient of thermal expansion (CTE) for Sm0.8B6 and Sm1 – xLaxB6 (x = 0, 0.1, 0.22, and 0.5). The minimum position of the CTE of samarium hexaboride as a function of the degree of lanthanum doping is determined. The obtained dependence allows one to predict the CTE minimum position for Sm1 – xLaxB6 compounds in the temperature range from 40 to 180 K and to optimize the developed composite invar materials, where the positive CTE of the functional material is compensated by the negative CTE of the valence-unstable system.
- ПубликацияОткрытый доступAnalysis of anomalous negative magnetic contribution to thermal expansion in Sm0.80B6 and pseudobinary compounds Sm1-xLaxB6 (x = 0, 0.10, 0.22, 0.50)(2019) Serebrennikov, D. A.; Clementyev, E. S.; Alekseev, P. A.; Алексеев, Павел Александрович© 2017 Elsevier B.V. This study is the first attempt to apply the two-level Weiss model for the invar alloy to intermediate-valence samarium systems. This model is instrumental in giving a quantitative characterisation of the anomalous magnetic contribution to the coefficient of thermal expansion (CTE) of Sm0.80B6 and Sm1-xLaxB6 (x = 0, 0.10, 0.22, 0.50). A good agreement between the experimental and calculated magnetic contributions to the CTE is achieved for Sm0.78La0.22B6 over the temperature range from 0 K to 210 K. In other systems, a good fit is obtained over shorter temperature ranges. The model parameters and the dependence of the CTE minimum on the level of lanthanum doping in SmB6 are presented.