Vibration-driven thermal transition in binuclear spin crossover complexes

An Ising-like model including the effect of intramolecular vibrations is proposed to investigate Fe(II) binuclear spin crossover complexes, especially in the situation where it allows the assessment of the conditions under which cooperative exchange interactions are weak enough to favor a vibration-...

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Bibliographic Details
Published in:The European physical journal. B, Condensed matter physics Condensed matter physics, 2012-06, Vol.85 (6), Article 205
Main Authors: Metatla, A., Latelli, H., Nicolazzi, W., Bousseksou, A.
Format: Article
Language:English
Subjects:
Analysis
Complex Systems
Condensed Matter Physics
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Exact sciences and technology
Fluid- and Aerodynamics
Magnetic properties and materials
Magnetically ordered materials: other intrinsic properties
Physics
Physics and Astronomy
Regular Article
Solid State Physics
Spin crossover
Vibration
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Summary:An Ising-like model including the effect of intramolecular vibrations is proposed to investigate Fe(II) binuclear spin crossover complexes, especially in the situation where it allows the assessment of the conditions under which cooperative exchange interactions are weak enough to favor a vibration-driven mechanism for the thermal transition. In particular, two spin states (LS-LS, LS-HS or HS-HS where LS and HS stand for low-spin and high-spin respectively) must be quasi-degenerate. Whatever the equi-energy scenario, the effect of molecular vibrations on the groundstate appears in the low temperature region, where a deviation from the low frequency approximation of the standard Ising-like model is observed. Thirteen quasi-equi-energy situations lead to three possible vibronic groundstates at T = 0 K, from which the thermal evolution of the HS fraction presents a similar trend as mononuclear systems. However, binuclear systems permit to generate a HS-LS vibronic groundstate. For this latter case the application of pressure, known to drastically affect the spin transition, is suggested to reveal a two-step behavior according to a LS-LS, HS-LS HS-HS scheme. Intramolecular coupling between the two metallic centres and intermolecular cooperativity few influence the spin transition curves due to a difference of the temperature ranges between the effects of molecular vibrations and spin crossover phenomenon.
ISSN:1434-6028
1434-6036
DOI:10.1140/epjb/e2012-30132-1