Analysis of long-range interaction effects on phase transitions in two-step spin-crossover chains by using Ising-type systems and Monte Carlo entropic sampling technique

作者：Chiruta D^*; Linares J; Dahoo P R; Dimian M

来源：Journal of Applied Physics, 2012, 112(7): 074906.

DOI：10.1063/1.4756994

The analysis of two-step spin crossover phenomena in one-dimensional systems is performed in the framework of Ising-type model by using Monte Carlo entropic sampling technique. Both short-range and long-range interactions are considered in the Hamiltonian which also takes into account different degeneracies between the molecular states. The density of states associated to each macrostate is computed by using entropic sampling, via a biased Monte Carlo sampling technique, and the corresponding Ising-type Hamiltonian can thus be solved by using a self-consistent approach. By using this semi-analytical method, the effects of long-range interactions on phase transition driven by temperature variation in spin crossover chains have been investigated. Various types of spin crossover phenomena have been identified from gradual two-step transition to the one accompanied by multiple hysteresis loops, which was also recently observed experimentally. A metastable %26quot;plateau%26quot; has been observed at a high-spin fraction approximately equal to 1/2 for intermediate temperature region, but this plateau is not part of the low-to-high spin transition in strong cooperative systems and might be reached only by using special reversal curves or other external factors, such as light or pressure. In addition, a standard Monte-Carlo algorithm with Arrhenius dynamics is applied to this system in order to better understand its molecular behavior during the intermediate phase.

• 出版日期2012-10-1