Abstract:
The critical properties and magnetocaloric effect of perovskite manganite La0.67Ca0.33Mn1-xCoxO3 (x=0.03, 0.1 and 0.15) are investigated. Structural study using Reitveld refinement of X-ray diffraction pattern indicates an orthorhombic structure with Pnma space group for all compositions. The Curie temperature and magnetic moment decrease with increase of cobalt doping concentration and the samples exhibit characteristics of spin/cluster glass state which is evident from magnetization (zero field cooled and field cooled) vs temperature curves. The magnetic data is analyzed in the critical region using the modified Arrott plot method. The obtained values of critical exponents are in agreement with the values predicted by mean field interaction model. LCMCo0.03 compound shows a large magnetic entropy change (Delta S-M) of 4 J/kg K at a magnetic field of 50 kOe. The relative cooling power (RCP) is found to be about similar to 184 J/kg for LCMCo0.03 and similar to 114 J/kg in the case of LCMCo0.1 in a magnetic field change of 50 kOe. The field dependance of Delta S-M and RCP are showing a power dependence at their respective transition temperatures. An increase in resistance and a diminution of magnetic entropy change were observed as a consequence of Co doping. An enhanced magnetoresistance up to 87% and considerable magnetic entropy change were observed for these cobalt doped compounds.
