Second-order magnetic phase transition in orthorhombic Pr0.7Ca0.15Ba0.15MnO3

We have studied the critical behavior around the ferromagnetic–paramagnetic (FM–PM) phase transition (the Curie temperature, TC) of a polycrystalline manganite Pr0.7Ca0.15Ba0.15MnO3. The assessments based on Banejee׳s criteria reveals the sample undergoing a second-order magnetic phase transition. The use of the modified Arrott and Kouvel–Fisher methods determined the values of critical parameters TC≈117 K, β=0.403±0.024 and γ=1.242±0.033. With these values, magnetic-field dependences of magnetization at temperatures around TC (M–H–T curves) can be well described by the universal function of M ( H , ε ) = | ε | β f ± ( H / | ε | β + γ ) , where ε=(T−TC)/TC, and f+ and f− are regular functions for T>TC and T<TC, respectively. Compared with the theoretical models, the β value obtained in our work is located in between those expected for the mean-field theory and the 3D Heisenberg model, while the γ value is close to that expected for the 3D Ising model. Such results demonstrate the coexistence of short- and long-range FM orders in Pr0.7Ca0.15Ba0.15MnO3. This is ascribed to magnetic inhomogeneity caused by Ba2+- and Ca2+-rich regions, and the coexistence of FM and anti-FM interactions.