Abstract
In this report first we show, in a framework of the Ising-like model, a numerical simulation of a typical two step thermal transition obtained for a square lattice 12x12: a “first-step hysteresis” for a high spin fraction Nhs between 0 - 0,5 and at a higher temperature a “second-step hysteresis” with Nhs between 0.5 and 1. As long as we decrease the number of molecules the temperature range of the “second-step hysteresis” moves to a lower temperature, until is obtained, for a square of 4x4, a clear overlapped case with a three state behaviour. A detailed analysis on the role of the size system (4x4, 5x5, 6x6, 8x8 and 12x12) on the stability of this “Three state behaviour” is presented in this contribution. We study the influence of the surrounding environment for this specific thermal hysteresis. To solve the self-consistent equation related to the average value of the spin-operator <σ>, we use the density of the states calculated using a dynamic programming algorithm that will be presented in this paper.
Highlights
In order to find new materials that can be used for information storage, many European, Japanese and American laboratories are involved in research activities in the study of bistable molecular materials
A new challenging problem related to the Spin Crossover (SCO) nanoparticles[15,16,17,18,19,20,21] at nanoscale level has been highlighted, since the size of particles proved to play an important role in the cooperativity of the system, and the role of edge molecules
The core/shell ratio and the interaction between edge molecules with their surrounding are related to the hysteresis for very low numbers of molecules
Summary
In order to find new materials that can be used for information storage, many European, Japanese and American laboratories are involved in research activities in the study of bistable molecular materials. The core/shell ratio and the interaction between edge (or surface) molecules with their surrounding are related to the hysteresis for very low numbers of molecules. This special case is obtained for an "antiferromagneticlike" short-range interaction together with a "ferromagnetic-like" long-range interaction and an interaction between the molecules at the surface and the surrounding matrix.
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