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Электронная структура и магнитный фазовый переход в геликоидальных ферромагнетиках Fe-=SUB=-1-x-=/SUB=-Co-=SUB=-x-=/SUB=-Si
Author(s) -
А. А. Повзнер,
Alexander G. Volkov,
Т.А. Ноговицына
Publication year - 2018
Publication title -
fizika tverdogo tela
Language(s) - English
Resource type - Journals
eISSN - 1726-7498
pISSN - 0367-3294
DOI - 10.21883/ftt.2018.02.45372.232
Subject(s) - condensed matter physics , ferromagnetism , magnetization , paramagnetism , electron , materials science , electronic structure , negative thermal expansion , thermal expansion , physics , magnetic field , quantum mechanics , metallurgy
AbstractLSDA + U + SO calculations of the electronic structure of helicoidal Fe_1 - x Co_ x Si ferromagnets within the virtual crystal approximation have been supplemented with the consideration of the Dzyaloshinski-Moriya interaction and ferromagnetic fluctuations of the spin density of collective d electrons with the Hubbard interactions at Fe and Co atoms randomly distributed over sites. The magnetic-state equation in the developed model describes helicoidal ferromagnetism and its disappearance accompanied by the occurrence of a maximum of uniform magnetic susceptibility at temperature T _ C and chiral fluctuations of the local magnetization at T > T _ C . The reasons why the magnetic contribution to the specific heat at the magnetic phase transition changes monotonically and the volume coefficient of thermal expansion (VCTE) at low temperatures is negative and has a wide minimum near T _ C have been investigated. It is shown that the VCTE changes sign when passing to the paramagnetic state (at temperature T _ S ).

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