Effects of Mn site substitution on magnetic ordering and critical behavior in Nd0.67Sr0.33MnO3 manganite

In this study, we investigated the structural, magnetic order, and critical exponent behaviors for substitutions of 3d transition elements (Cr, Fe, and Co) at the Mn site in Nd0.67Sr0.33MnO3. Rietveld refinement confirmed that all of the compounds had an orthorhombic crystal structure. X-ray absorption spectroscopic analysis confirmed minor variations in the Mn3+/Mn4+ ratio due to doping with transition metal elements at the Mn site. The parent and Cr-substituted compounds obeyed the Curie-Weiss law, whereas the other compounds did not, thereby indicating the presence of some ferromagnetic clusters within the paramagnetic matrix. The critical behavior of the system was analyzed using the modified Arrott plot method and critical isotherm analysis. The critical exponents β and γ calculated for the parent compound were consistent with the predictions based on the tricritical model, whereas the critical exponents determined for the substituted compounds were close to the mean field model. The critical exponents governing the magnetic phase transition calculated from the field dependence of the magnetic entropy change were in good agreement with those obtained from the modified Arrott plot and critical isotherm analysis.