Spin- Crossover in Molecular Crystals: An Electron- Coupled Local Vibrations Model

  • C. Rodríguez-Castellanos Faculty of Physics, University of Havana, 10400 Havana, Cuba
  • Y. Plasencia-Montesinos Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada (CICATA−Legaria), Instituto Politécnico Nacional, 11500 Ciudad de México, Mexico
  • E. F. Reguera-Ruiz Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada (CICATA−Legaria), Instituto Politécnico Nacional, 11500 Ciudad de México, Mexico

Abstract

A model of eg electrons at octahedral sites coupled to local vibrational “breathing” modes interacting with its near neighbors is proposed to describe spin-crossover (SCO) in molecular crystals. Decoupling vibrations leads to an effective electron Hamiltonian with renormalized site energies, where ferromagnetic and antiferromagnetic, short range and long range electron-electron interactions arise in a natural way. An exact analytic expression for the free energy functional is derived. A phase diagram for homogenous phases, describing the basic phenomenology of SCO is obtained and the transition temperatures are expressed in terms of model parameters. Under appropriate conditions, two-step transitions are found to take place for systems with both, short range and long range interactions. Stability with respect to spatial fluctuations is discussed.

Published
Dec 15, 2018
How to Cite
RODRÍGUEZ-CASTELLANOS, C.; PLASENCIA-MONTESINOS, Y.; REGUERA-RUIZ, E. F.. Spin- Crossover in Molecular Crystals: An Electron- Coupled Local Vibrations Model. Revista Cubana de Física, [S.l.], v. 35, n. 2, p. 91-96, dec. 2018. ISSN 2224-7939. Available at: <http://www.revistacubanadefisica.org/index.php/rcf/article/view/RCF_2018_35_91>. Date accessed: 20 jan. 2019.
Section
Original Articles