Magnetic Materials of La2/3-xEuxCa1/3MnO3 Manganites for the Refrigeration Application from 150 to 225 K

Abstract

The phase structure and magnetic and magnetocaloric effect (MCE) properties have been studied in La_2/3-xEu_xCa_1/3MnO₃ (0 ≤ x ≤ 0.08) manganites prepared by conventional solid-state reaction. There is no miscellaneous phase in the samples, which are analyzed by the Rietveld refinement method. The refinement data shows the lattice decreases gradually with smaller radius of Eu³⁺ substitution. The Curie temperature of the material is continuity distributed from 150 to 225 K. Large magnetic entropy changes (ΔS_M) are obtained with Eu³⁺ substitution, the highest value of −ΔS_M is 4.93 J·kg⁻¹ K⁻¹ in the magnetic field change at 2 T, and the relative cooling power (RCP) value is around ~ 110 J·kg⁻¹. The samples undergo a first-order magnetic phase transition with small hysteresis, for x = 0.00, 0.02, when x ≥ 0.4, the samples under a second-order magnetic phase transition. The results show that the substitution of Eu³⁺ can be used to modify the Curie temperature and obtain a continuous operating temperature interval, without sacrificing the MCE. The large MCE performance, continuous working temperature interval, and high cooling efficiency make our samples be used for the application of magnetic refrigeration.