Thermodynamics of magnetism for par ticles with small number of elements.

VOGEL E. E.; VALDES, JULIO; SARAVIA, G.; VARGAS, P.; RAMIREZ PASTOR, A. J.; CENTRES, P. M.

Congreso; Entropy 2018 ? From Physics to Information Sciences and Geometry; 2018

The statistical mechanical treatment of magnetism is examined using the wellknown Ising and Potts (clock) models for the case of very small systems. Sincethe main laws of thermodynamics and statistical physics were derived for varylarge systems in what is usually called the thermodynamic limit (TL), severalquestions arise when these concepts are used for particles with under onethousand elements (magnetic centers in our case). However, presenttechnology allows us to deal with these molecular or subnanoscopic systems[1] where some of the assumptions valid in the TL are not valid in the usualway [2]. Computer simulations for simple examples based on the Ising and theclock models are carried out. We review the concepts of ergodic separation,magnetization reversal, average magnetization, critical temperature andothers as the systems become very small. We identify features that needspecial care for systems with few magnetic centers. The results are discussedby means of two examples, namely, two magnetic sensors with two differentpurposes