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 (T-C) 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 (Delta S-M) for the samples were determined. Under an applied field of 15.0 kOe, the maximum DSM (named Delta S-max) achieved around T-C for x = 0.0 and 0.05 are about 5.9 and 4.8 J . kg(-1) . K-1, respectively. While the linewidth of Delta S-M curves (delta T-FWHM) 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 delta T-FWHM, the samples still exhibit the first-order phase transition. If combining these samples for magnetic refrigeration, the temperature range can be used lying in between 210 and 275 K, where Delta S-max values are stable at about 3.5 J . kg(-1) . K-1. RCP is thus about 228 J/kg, and comparable to that of some magnetocaloric alloys. This makes La0.7Ca0.3Mn1-xCoxO3 compounds suitable to magnetic-refrigeration applications. (C) 2012 American Institute of Physics. [doi:10.1063/1.3670974]