Structure, magnetocaloric and critical properties of layered La2Sm0.4Sr0.6Mn2O7 perovskite

We report the structure, magnetocaloric effect, and critical phase transition in the manganite La2Sm0.4Sr0.6Mn2O7 (LSSMO) synthesized by a sol-gel method. X-ray diffraction together with Rietveld refinement show that the sample crystallizes in a Sr3Ti2O7-type tetragonal structure with a space group of I4/mmm. This compound undergoes a second-order ferromagnetic (FM) to paramagnetic phase transition at TC=348 K and shows strong FM properties below the TC. Based on the data of isothermal magnetization measured around the TC and Maxwell's relation, we calculated the maximum magnetic entropy change (-ΔSMmax) to be 4.69 J kg−1 K−1 and the relative cooling power to be 233.9 J kg−1 for a μ0ΔH=5 T magnetic field variation. These results indicate that LSSMO can be considered as a potential candidate material for application in magnetic refrigeration above room temperature. The critical behavior near the TC was studied through the analysis of the magnetic field dependence of the magnetic entropy change and Widom's scaling relation. The exponent values estimated in this work are fairly close to those theoretically predicted by mean field theory (β=0.5, γ=1.0, and δ=3.0), revealing that long-range FM ordering exists in LSSMO. Scaling law theory also confirms the validity of the deduced critical exponents.