CRITICAL PARAMETERS IN PERROVSKITE La0.7Sr0.3Mn1-xMxO3 (x=0, 0.05; M=Al, Ti)

Abstract

The perrovskite La_0.7Sr_0.3Mn_1-xM_xO₃ (x = 0; 0.05; M = Al, Ti) was fabricated by conventional solid state physic. The critical parameters have been derived by several techniques ussing experimental magnetic data. The results show that substitution Al and Ti for Mn in La_0.7Sr_0.3MnO₃ reduces temperature of ferro-parramangetic phase transition to 334 K; 310.6 K, respectively. The critical parameters imply that magnetic interaction in materials also changes from 3D Ising to 3D Heisenberg and tricritical mean field models with 5% Mn substituted by Al and Ti respectively. Specifically, using the modified Arrott plots (MAP) method, with x = 0, the critical values are defined as β = 0.3217; g = 1.126, these values are close to 3D Ising model. However, with 5% Al replacing Mn we have obtained β = 0.4896; g = 1.0743, these values are close to the Mean-field model. Whereas with 5% Ti replaced Mn, β = 0.3224; g = 1.1291, these values is more suitable for tricritical mean - field model. This proves that the long-distance interaction is mainly formed in the sample La_0.7Sr_0.3Mn_0.95Al_0.05O₃. The values of the critical parameters obtained by the Kouvel-Fisher method show that there is not much difference from the MAP method. In addition, we have shown that the critical exponents are in good agreement with the Scalling theory.