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Magnetic quantum phase transitions and entropy in van vleck MAGNET

Репозитарій Національного Авіаційного Університету

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Title Magnetic quantum phase transitions and entropy in van vleck MAGNET
 
Creator Лаванов, Геннадій Юрійович
 
Subject magnetic
phase
transitions
quantum
 
Description Field-induced magnetic quantum phase transitions in the Van Vleck paramagnet with easyplane
single-ion anisotropy and competing Ising exchange between ions with the spin S=1
have been studied theoretically. The description was made by minimizing the Lagrange
function at zero temperature (Т = 0) and the free energy at T  0. Stable and unstable
solutions of equations corresponding to the case T  0 asymptotically transform into those
following from the Lagrange function at Т = 0. First-order phase transitions from the Van
Vleck paramagnet state into the ferromagnet one were found to take place at a sufficiently
high single-ion anisotropy. The entropy of such a magnet was shown to grow with its
magnetization, as it occurs for antiferromagnets. At the point of quantum phase transition, the
entropy has a jump, which magnitude depends on the ratio between the Ising exchange and
anisotropy constants, as well as on the temperature. The described magnetic phase transition
was supposed to be accompanied by the magnetocaloric effect. In the case when the Ising
exchange dominates over the single-ion anisotropy, the magnetization reversal of
ferromagnetic state by an external field was shown to be a phase transition of the first kind,
which does not belong to orientational ones and which should be regarded as a quantum
order-order phase transition.
 
Date 2018-06-13T18:57:39Z
2018-06-13T18:57:39Z
2016-10-15
 
Type Article
 
Identifier Journal of Magnetism and Magnetic Materials Volume 416, 15 October 2016, Pages 466-474; DOI: 10.1016/j.jmmm.2016.05.017
http://er.nau.edu.ua/handle/NAU/35238
 
Language en_US
 
Format application/pdf
 
Publisher Elsevier
 

Технічна підтримка: НДІІТТ НАУ