Magnetic phase diagram for a nonextensive system: Experimental connection with manganites

In the present paper we make a thorough analysis of a classical spin system, within the framework of Tsallis nonextensive statistics. From the analysis of the generalized Gibbs free energy, within the mean-field approximation, a paramagnetic-ferromagnetic phase diagram, which exhibits first- and second-order phase transitions, is built. The features of the generalized and classical magnetic moment are mainly determined by the values of q, the nonextensive parameter. The model is successfully applied to the case of ${\mathrm{La}}_{0.60}{\mathrm{Y}}_{0.07}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ manganite. The temperature and magnetic field dependence of the experimental magnetization on this manganite are faithfully reproduced. The agreement between rather ``exotic'' magnetic properties of manganites and the predictions of the q statistics comes to support our initial claim that these materials are magnetically nonextensive objects.