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

We report the magnetic, magnetocaloric properties and critical behavior near transition temperature in La0.78Pb0.22MnO3 perovskite manganite, prepared by solid state reaction method. Temperature dependence of magnetization exhibits a ferromagnetic to paramagnetic transition (TC) at 292 K. Close to this transition, a maximum magnetic entropy change (−ΔSMmax) 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 (TC, β, γ, and δ) have been determined. The estimated critical exponents (β=0.246, γ=0.929 and δ=4.49 at TC=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-μ0H-T) data around TC are found to collapse into two curves by obeying the single scaling equation M(μ0H,ε)=(ε)βf±(μ0H/εβ+γ) where ε=T−TC/TC, f+ above and f− below TC, and confirm that the obtained values of β, γ and δ are reasonably accurate and unambiguous.