Effect of synthesis techniques on structural, magnetocaloric and critical behavior of Pr0.6Ca0.1Sr0.3Mn0.975Fe0.025O3 manganites

Abstract

The effect of synthesis techniques on structural, magnetocaloric and critical behavior in Pr0.6Ca0.1Sr0.3Mn0.975Fe0.025O3 (PCSMFO) sample has been investigated. The sample was synthesized by two different methods: the solid-state reaction (SS) and Pechini sol–gel method (SG). X-ray diffraction analysis shows that our sample crystallizes in the orthorhombic structure with the Pbnm space group for both methods. Magnetic measurements show that our sample exhibits a ferromagnetic (FM)–paramagnetic (PM) transition with increasing temperature. The Curie temperature (TC) and magnetocaloric effect (MCE) of SS sample and SG sample were studied. A large magnetocaloric effect around Curie temperature is observed in our sample prepared by both methods. Moreover, the critical exponents β, γ, and δ determined as using the modified Arrott-plot (MAP), the Kouvel–Fisher method (KF), as well as the critical isotherm (CI) analysis. In both studied techniques, the Arrott plots show that the phase transition is of the second-order. Moreover, for the sample which is prepared by solid-state, the estimated critical exponents are close to those expected for mean-field model. For the SG sample, these exponents are close to those expected for 3D-dimensional Heisenberg and the value of critical exponents γ decreased and approached the 3D-Ising (γ=1.24). Interestingly, the change of the universality class can be explained by the reduction of grain size (D). The reduction of the grain size tends to create a transition phase from a long-range to short-range order in the system. These results suggest that the physical properties of our sample are strongly depended on the synthesis techniques.