Effect of Ru-Doping on Magnetocaloric Effect in Pr Based Charge Ordered Manganites

It is shown that charge-orbital ordered antiferromagnetic state of the parent compound (x = 0) in Pr_0.5Ca_0.5Mn_1-xRu_xO₃ series is destabilized and ferromagnetism is induced by Ru doping, as small as 3%, at the Mn site. The ferromagnetic transition temperature (T_C) increases with Ru content from T_C = 213 K for x = 0.03 to 239 K for x = 0.1 but the field dependence of magnetization does not show metamagnetic transition above or below T_C unlike Pr_0.5Ca_0.5Mn_1-xRu_xO₃. The change in magnetic entropy (¿S_M) is the largest for x = 0.03 (¿S_M = -4.2 J/kg K at 213 K for ¿H = 5 T) and decreases with increasing Ru content (¿S_M = -3.8 J/kg K at 221K and -3.4 J/kg K at 239 K for ¿H = 5 T, for x = 0.05 and 0.10, respectively). However, the relative cooling power increases with Ru content from 284.9 J/kg for x = 0.03 to 303.6 J/kg for x = 0.1. The large magnetic entropy change found in x = 0.03 and the absence of high field hysteresis in M-H curves make the Ru-doped samples suitable candidates for magnetic refrigeration.