Effect of Ru-substitution on electrical and magnetocaloric properties of

It is shown that the charge-orbital ordered antiferromagnetic insulating state of the parent compound ( y = 0 ) in Nd0.5Ca0.5Mn1−yRuyO3 ( y = 0 , 0.03, 0.05, & 0.10) series is destabilized and a ferromagnetic metallic state is induced by Ru substitution as small as 3%. The ferromagnetic transition temperature ( T C ) increases with Ru content from 215 K ( y = 0.03 ) to 255 K ( y = 0.10 ) . The magnetic entropy change ( Δ S m ) of y = 0 changes sign from negative to positive as the temperature is lowered below the charge ordering temperature. However, Δ S m is negative and exhibits a peak close to T C in Ru-doped samples. The peak values of Δ S m are − 0.33 , − 3.8 , − 3.6 , and −3.5 J kg−1 K−1 for y = 0 , 0.03, 0.05, & 0.10 respectively, for a field change of Δ H = 5  T. The relative cooling power (RCP) decreases with increasing Ru content from 268 J/kg for x = 0.03 to 234 J/kg for x = 0.10 for Δ H = 5  T whereas the y = 0 sample shows 17 J/kg. The large RCP and Δ S m found in Ru-substituted samples will be interesting for magnetic refrigeration below room temperature.