Question

Magnetocaloric properties of Eu1â’xLaxTiO3 (0.01 ≤ x ≤ 0.2) for cryogenic magnetic cooling

Answer 1

The structural, magnetic and magnetocaloric properties of La0.7Ba0.2Ca0.1Mn1−xAlxO3 (0 ≤ x ≤ 0.1) perovskite manganite oxides have been investigated. X-ray diffraction (XRD) analysis using Rietveld refinement has shown that all of the samples under investigation crystallize with a rhombohedric structure in the Rc space group (N°167). Paramagnetic (PM) to ferromagnetic (FM) transitions have been observed in all of the synthesized samples. In addition, the maximum magnetic entropy change (ΔSmaxM) for the x = 0 sample was found to reach ∼5.8 J kg−1 K−1 under an applied magnetic field of 5 T, which is sufficient for potential applications in magnetic refrigeration. For the same applied magnetic field (μ0H = 5 T), the relative cooling power (RCP) value is found to be 167 J kg−1. The critical properties of manganites La0.7Ba0.2Ca0.1Mn1−xAlxO3 (0 ≤ x ≤ 0.1) are investigated through various techniques, such as modified Arrott plots, Kouvel–Fisher methods and critical isotherm analyses around the paramagnetic–ferromagnetic phase transition (Tc). The values of critical exponents, derived from magnetic data using the above methods, yield 0.246 ≤ β ≤ 0.253, 1.01 ≤ γ ≤ 1.12 and 4.76 ≤ δ ≤ 4.9 with a Tc of 300–350 K. The exponent values are close to those expected for tricritical mean field model ferromagnets with short-range dipole–dipole interactions.