Influence of Pb Doping on the Magnetocaloric Effect and Critical Behavior of (La_0.9Dy_0.1)_0.8Pb_0.2MnO₃

Abstract

We used the modified Arrott plot method to analyze the magnetic field dependence of the magnetization, M(H), for a perovskite-type manganite (La_0.9Dy_0.1)_0.8Pb_0.2MnO₃, and determined the critical parameter values T _C = 248.4 K, β = 0.484 ± 0.002, γ = 0.961 ± 0.012, and δ = 2.90 ± 0.01. With these exponent values, the M(H) data around T _C fall on two universal branches of a scaling function M(H,ε) = |ε|^β f _±(H/|ε|^β + γ), where ε = (T − T _C)/T _C is the reduced temperature, f ₊ for T > T _C and f ₋ for T < T _C. Comparing with theoretical models, the exponent values obtained in our work are quite close to those expected from mean-field theory (with β = 0.5, γ = 1, and δ = 3). This reveals nearly long-range ferromagnetic order existing in (La_0.9Dy_0.1)_0.8 Pb_0.2MnO₃. From the M(H) data, we also found that, around the ferromagnetic–paramagnetic phase-transition temperature (T _C), the magnetic entropy change reaches a maximum value (|δS _max|) of about 1.1 J kg⁻¹ K⁻¹ for H = 10 kOe, corresponding to relative cooling power (RCP) of 50 J/kg. In addition to the above investigation, the temperature dependence of the magnetization, remanent magnetization (M _r), and coercivity (H _c) were recorded to learn about the physical processes taking place in (La_0.9Dy_0.1)_0.8Pb_0.2MnO₃.