Effect of Ru-substitution on electrical and magnetocaloric properties of Nd0.5Ca0.5MnO3

Abstract

It is shown that the charge-orbital ordered antiferromagnetic insulating state of the parent compound (y=0) in Nd0.5Ca0.5Mn 1-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 (TC) increases with Ru content from 215 K (y=0.03) to 255 K (y=0.10). The magnetic entropy change (ΔSm) of y=0 changes sign from negative to positive as the temperature is lowered below the charge ordering temperature. However, ΔSm is negative and exhibits a peak close to TC in Ru-doped samples. The peak values of ΔSm 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 ΔH=5 T. The relative cooling power (RCP) decreases with increasing Ru content from 268 Jkg for x=0.03 to 234 Jkg for x=0.10 for ΔH=5 T whereas the y=0 sample shows 17 Jkg. The large RCP and ΔSm found in Ru-substituted samples will be interesting for magnetic refrigeration below room temperature. © 2010 Elsevier Ltd. All rights reserved.