Cooperativity in spin-crossover transition in metalorganic complexes: Interplay of magnetic and elastic interactions

Abstract

It is of significant technological interest to have an understanding of cooperativity in spin-crossover phenomena observed in metalorganic polymeric complexes. Microscopic origin of this cooperativity has been discussed in literature primarily in terms of elastic interactions. Through Monte Carlo simulation of the model Hamiltonian we show that the superexchange interactions between localized magnetic moments at spin-crossover sites can play a crucial role in cooperativity, depending on the nature of the elastic interactions. While in the case of the effective elastic interaction of ferroelastic nature, inclusion of the above-mentioned exchange interaction produces quantitative changes in the hysteresis loop, for effective elastic interaction of antiferroelastic nature, the existence of hysteresis is found to be dictated entirely by the magnetic exchange interaction. Considering the example of a real material, namely Fe-triazole, employing the material-specific density functional theory calculation, we show the later scenario to be true for these systems. Our study should motivate further investigation on the role of magnetic exchanges in metalorganic polymers.