2D Spin Crossover Nanoparticles described by the Ising-like model solved in Local Mean-Field Approximation

Salah Eddine Allal,Pierre Richard Dahoo,Jorge Linares,F De Zela,K Boukheddaden

doi:10.1088/1742-6596/936/1/012052

Abstract

Some six-coordinate iron (II) coordination compounds exhibit thermal-, optical-, electrical-, magnetic- and pressure-induced switching between the diamagnetic low-spin (LS, S=0) and the paramagnetic high-spin (HS; S=2) states [1]. This may lead to potential application of these complexes in molecular devices such as temperature and pressure sensors [2]. An Ising-like model has been proposed to explain the occurrence of the thermal hysteresis behaviour [3,4] of this switchable solids. In this contribution, the local mean field approximation is applied to solve the Hamiltonian modelling interactions pertaining to 2D nanoparticles embedded in a magnetically-inactive matrix.

Highlights

It is very well known that spin-transition phenomena are related to the thermodynamic competition between high-spin (HS) and low-spin (LS) states of spin-crossover (SCO) molecules
We deal with a local mean field approximation (LMFA), which takes into account for the dependence of the number of neighbors on whether the molecules are in the bulk or at the border of the lattice
The advantage of the LMFA is the possibility to study the effect of the shape of the compound on the the thermal properties, through the change of the number of “edge” molecules, which increases for a rectangular case, for example compared to the square with the same total number of sites

Summary

Introduction

It is very well known that spin-transition phenomena are related to the thermodynamic competition between high-spin (HS) and low-spin (LS) states of spin-crossover (SCO) molecules. We deal with a local mean field approximation (LMFA), which takes into account for the dependence of the number of neighbors on whether the molecules are in the bulk or at the border (or on the surface) of the lattice.

Results

Conclusion