Disorder-driven phase transition in La0.37D0.30Ca0.33MnO3 (D = Bi, Sm) manganites

In the present work we report the structural, electron spin resonance (ESR) and magnetic properties of La0.37D0.30Ca0.33MnO3 (D = Bi, Sm) manganites synthesized by sol-gel method. The critical behavior at the critical point, where the system undergoes phase transition from paramagnetic (PM) to ferromagnetic (FM) state, is investigated by using modified-Arrott plots, Kouvel-Fisher method and critical isotherm analysis. Both the samples show second-order phase transition near the critical point. The decrease in magnetization (M), Curie temperature (TC), evolution of spin or cluster glass behavior and the nature of second-order phase transition compared to the first-order transition reported in the literature for La0.67Ca0.33MnO3 are ascribed to disorder caused by the size mismatch of the A-site cations with Bi and Sm doping at La-site.