Evidences for Tsallis non-extensivity on CMR manganites

¹ Centro Brasileiro de Pesquisas Físicas - Rua Dr. Xavier Sigaud 150 Rio de Janeiro-RJ 22290-180, Brazil
² Departamento de Física, Universidade Federal do Espirito Santo Vitória-ES, 2906-900, Brazil

Corresponding author: marior@cbpf.br

Received: 1 October 2001
Accepted: 14 January 2002

Abstract

We found, from the analysis of M vs.  T curves of some manganese oxides (manganites), that these systems do not follow the traditional Maxwell-Boltzmann statistics, but the Tsallis statistics, within the normalized formalism. Curves were calculated within the mean-field approximation, for various ferromagnetic samples and the results were compared to measurements of our own and to various other authors's published data, chosen at random from the literature. The agreement between the experimental data and calculated M_q vs. curve, where is an effective temperature, is excellent for all the compounds. The entropic parameter, q, correlates in a simple way with the experimental value of , irrespective of the chemical composition of the compounds, heat treatment or other details on sample preparation. Examples include q<1 (superextensivity), q=1 (extensivity) and q>1 (subextensivity) cases.