Tuning of Curie Temperature and Magnetocaloric Effect via Annealing Condition Change in La 0.8K0.2MnO 3 Manganites

In this paper, we report on the structural, magnetic and magnetocaloric properties of La 0.8K0.2MnO 3 manganites annealed at different temperatures in the form of powder. The analyses of X-ray diffraction patterns indicate that the crystallographic structure is unchanged when the annealing temperature increases from 800 to 1200 ∘C. The annealing conditions have obvious influences on the Curie temperature and isothermal entropy change. With an applied field change of 5 T, the maximum values of isothermal entropy changes are found to be 3.7 J/kg K at 283 K, 3.4 J/kg K at 298 K, 4.0 J/kg K at 308 K, 4.3 J/kg K at 318 K, and 4.6 J/kg K at 293 K for Ta= 800, 900, 1000, 1100, and 1200 ∘C, respectively. The results imply that the change of annealing conditions is an applicable way for optimizing the Curie temperature and magnetocaloric effect for such potassium-doped manganites.