Magnetic Properties and Spin Crossover in Transition Metal Oxides with d 5 Ions at High Pressures

Тип публикации: статья из журнала

Год издания: 2019

Идентификатор DOI: 10.1134/S1063776119120185

Аннотация: Abstract: We analyze the influence of cooperative effects on the magnetic properties and spin crossover between the high-spin (HS) term S = 5/2 and low-spin (LS) term S = 1/2 in Mott–Hubbard dielectrics with 3d5 ions under high pressures. Two cooperation mechanisms (superexchange interaction and effective interaction via the elastic system) are considered. The sign of the exchange interaction changes because of the crossover from the antiferromagnetic in the HS state to the ferromagnetic in the LS state. In view of the large difference between the ionic radii of the HS and LS states, the systems with spin crossover acquire an additional strong coupling via the elastic system. Using the Hubbard operator representation and considering the electronic states of the two terms simultaneously, we obtain the effective Hamiltonian with allowance for the cooperative effects. The magnetic phase diagram and the spin crossover are investigated in the mean field approximation. It is shown that the inclusion of cooperative effects at low temperatures leads to a first-order phase transition between the antiferromagnetic HS state and the ferromagnetic LS state. At higher temperatures, more complicated sequences of phase transitions are possible upon an increase in pressure, including the HS paramagnet–HS antiferromagnet–LS paramagnet and HS antiferromagnet–LS paramagnet–LS ferromagnet transitions. © 2019, Pleiades Publishing, Inc.

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Издание

Журнал: Journal of Experimental and Theoretical Physics

Выпуск журнала: Vol. 129, Is. 6

Номера страниц: 1062-1069

ISSN журнала: 10637761

Издатель: Pleiades Publishing

Авторы

  • Orlov Yu S. (Russian Acad Sci, Fed Res Ctr, Kirensky Inst Phys, Krasnoyarsk Sci Ctr, Krasnoyarsk 660036, Russia)
  • Nikolaev S.V (Russian Acad Sci, Fed Res Ctr, Kirensky Inst Phys, Krasnoyarsk Sci Ctr, Krasnoyarsk 660036, Russia)
  • Ovchinnikov S.G. (Siberian Fed Univ, Krasnoyarsk 660041, RussiaArticle)

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