Magnetocaloric effect and critical behavior in Fe-doped La0.67Sr0.33Mn1−xFexO3 manganites

In this paper we report on the magnetocaloric effect and critical behavior of La0.67Sr0.33Mn1−xFexO3 (x=0, 0.05, 0.1 and 0.2) manganites. The samples were prepared by the sol-gel method. X-ray diffraction patterns indicate that the Fe-doped manganites crystallize in a single phase with the rhombohedral structure. The Curie temperature decreases monotonously from 355 K to 100 K as the Fe concentration increases from 0 to 0.2. The maximum values of isothermal entropy change (−ΔST,max) are found to be 1.66, 0.59, 0.79 and 0.42 J/kg K under a magnetic field change of 3 T for x=0, 0.05, 0.1 and 0.2, respectively. Although the −ΔST,max maxima are low, the manganites still exhibit significant refrigeration capacity (39-163 J/kg). The critical behaviors of the manganites have been studied by means of modified Arrott plot, Widom scaling and Kouvel-Fisher methods. The obtained critical exponents indicate that the Fe-doping level has significant influences on the critical behavior of the phase transition in the Fe-doped manganites.