Normal and inverse magnetocaloric effect and short-range ferromagnetic interaction in (Pr, Sm)0.5Sr0.5MnO3 phase separated manganite

The dependence of critical phenomenon on disorder induced by R/A-site cational size mismatch in polycrystalline manganite Pr0.5-xSmxSr0.5MnO3 (x = 0.25) has been investigated by means of bulk magnetization M (H, T) in the vicinity of the ferromagnetic-paramagnetic phase-transition. The critical exponents characterizing this second order phase transition, have been obtained using different methods such as modified Arrott plot, Kouvel-Fisher plot, critical isotherm analysis and field dependence of magnetocaloric effect. Moreover, the self-consistency and reliability of obtained critical exponents are verified by the Widom scaling law and scaling equations. We demonstrate that at x = 0.25 doping level, the beta value match well with those theoretically predicted for the 3D-Heisenberg model, while the gamma value is close to that expected for the 3D-Ising model. This suggests that the presence of R/A-site disorder in the system must be taken into account to fully describe the magnetism of phase separated manganites. Hence, the short-range ferromagnetic originates from phase inhomogeneity and evolves with addition of disorder depending on Sm content. Moreover, this sample also shows a coexistence of normal and inverse magnetocaloric effect. (C) 2016 Elsevier B.V. All rights reserved.