Critical parameters near the ferromagnetic–paramagnetic phase transition in La0.7A0.3(Mn1−xbx)O3 (A=Sr; B=Ti and Al; x=0.0 and 0.05) compounds

Abstract The critical parameters provide important information concerning the interaction mechanisms near the paramagnetic-to-ferromagnetic transition. In this paper, we present a thorough study for the critical behavior of La 0.7 A 0.3 (Mn 1− x B x )O 3 ( A =Sr; B =Ti and Al; x =0.0 and 0.05) polycrystalline samples near ferromagnetic–paramagnetic phase transition temperature by analyzing isothermal magnetization data. We have analyzed our dc-magnetization data near the transition temperature with the help of the modified Arrot plot, Kouvel–Fisher method. We have determined the critical temperature T C and the critical parameters β , γ and δ . With the values of T C , β and γ , we plot M ×(1− T / T C ) − β vs. H ×(1− T / T C ) − γ . All the data collapse on one of the two curves. This suggests that the data below and above T C obey scaling, following a single equation of state. Critical parameters for x =0 and x Ti =0.05 samples are between those predicted for a 3D-Heisenberg model and mean-field theory and for x Al =0.05 samples the values obtained for the critical parameters are close to those predicted by the mean-field theory.