CRITICAL-BEHAVIOR NEAR THE FERROMAGNETIC-PARAMAGNETIC PHASE-TRANSITION IN LA0.8SR0.2MNO3

We have investigated the critical behaviour of a La0.8Sr0.2MnO3 polycr ystalline sample near its ferromagnetic-paramagnetic phase transition temperature by determining the critical exponents corresponding to var ious thermodynamical quantities. Such a study is very important and in teresting because this magnetic phase transition is associated with a simultaneous electronic phase transition, i.e. a metal-insulator trans ition. In this paper, we report our results on this magnetic phase tra nsition analysed through various techniques like the modified Arrott p lots, Kouvel-Fisher method, scaling-equation-of-state analysis and the critical magnetisation isotherm. The values deduced for the critical exponents are in good agreement with those predicted, theoretically, f or the mean field theory, indicating that the exchange interaction is of long-range type. (C) 1998 Elsevier Science B.V. All rights reserved .