Magnetic, magnetocaloric and critical behavior study of La0.78Pb0.22MnO3 manganite near room-temperature

Abstract We report the magnetic, magnetocaloric properties and critical behavior near transition temperature in La 0.78 Pb 0.22 MnO 3 perovskite manganite, prepared by solid state reaction method. Temperature dependence of magnetization exhibits a ferromagnetic to paramagnetic transition (T C ) at 292 K . Close to this transition, a maximum magnetic entropy change ( − Δ S M max ) of 4.31 J/kg K and a relative cooling power (RCP) of 238 J/K are determined at a field of 5 T. Experimental results revealed that this sample underwent a second-order phase transition. Using the modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis, the critical parameters (T C , β, γ, and δ) have been determined. The estimated critical exponents (β=0.246, γ=0.929 and δ=4.49 at T C =290.01 K) are found to be close to the tricritical mean-field model. These critical exponents fulfill the Widom scaling relation δ = 1 + γ / β , implying the reliability of our values. On the basis of the obtained critical exponents, the magnetization-field -temperature (M-μ 0 H-T) data around T C are found to collapse into two curves by obeying the single scaling equation M ( μ 0 H , e ) = ( e ) β f ± ( μ 0 H / e β + γ ) where e = T − T C / T C , f + above and f − below T C , and confirm that the obtained values of β, γ and δ are reasonably accurate and unambiguous.