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Abstract: In accordance with recent experiments the mean-field type theories predictthe presence of numerous metastable minima states in the rugged free-energylandscape of frustrated disordered magnets. This multiplicity of long-livedstates with lifetimes greater than $10^5 s$ makes the task to experimentallydetermine which of them has the lowest free energy and thus what thermodynamicphase the sample is in seem rather hopeless the more so as we do not know aprotocol such as field-cooling or zero-field-cooling leading to theequilibrium states. Nevertheless here we show in the framework of Landau-typephenomenological model that signatures of the mean-field equilibrium phasetransitions in such highly nonequilibrium systems may be found in the evolutionof the hysteresis loop form. Thus the sequence of transitions from spin-glassto mixed phase and to ferromagnetic one results in the changes from inclinedhysteresis loop to that with the developing vertical sides and to one with theperfectly vertical sides. Such relation between loop form and the location ofglobal minimum may hold beyond the mean-field approximation and can be usefulin the real experiments and Monte-Carlo simulations of the problems involvingrugged potential landscape. Also the very existence of the quasi-static loopsin spin glass and mixed phases implies that the known disorder-smoothing of thefirst-order transition can be always accompanied by the emergence of multiplemetastable states.



Autor: P.N. Timonin

Fuente: https://arxiv.org/



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