Large magnetocaloric effect for magnetic refrigeration from 210 to ∼275 K in La0.7Ca0.3Mn1−xCoxO3

We have studied the magnetic properties and magnetocaloric effect in La0.7Ca0.3Mn1−xCoxO3 (x = 0–0.05) prepared by conventional solid-state reaction. Magnetic measurements versus temperature revealed that both magnetization and the Curie temperature (TC) decreased gradually with increasing Co content (x); TC values are about 270 and 215 K for x = 0.0 and 0.05, respectively. Based on magnetic-field dependences of magnetization recorded at various temperatures, curves of the magnetic entropy change (ΔSM) for the samples were determined. Under an applied field of 15.0 kOe, the maximum ΔSM (named ΔSmax) achieved around TC for x = 0.0 and 0.05 are about 5.9 and 4.8 J · kg−1 · K−1, respectively. While the linewidth of ΔSM curves (δTFWHM) changes from 12 to 16 K with varying x from 0 to 0.05, the relative cooling power (RCP) is in between 67 and 78 J/kg. Though an increase in Co content widens δTFWHM, the samples still exhibit the first-order phase transition. If combining these samples for magnetic refrigeratio...