Please use this identifier to cite or link to this item: http://er.nau.edu.ua:8080/handle/NAU/35238
Title: Magnetic quantum phase transitions and entropy in van vleck MAGNET
Authors: Лаванов, Геннадій Юрійович
Keywords: magnetic
phase
transitions
quantum
Issue Date: 15-Oct-2016
Publisher: Elsevier
Citation: Journal of Magnetism and Magnetic Materials Volume 416, 15 October 2016, Pages 466-474; DOI: 10.1016/j.jmmm.2016.05.017
Abstract: 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.
URI: http://er.nau.edu.ua:8080/handle/NAU/35238
Appears in Collections:Наукові публікації кафедри загальної фізики

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