Magneto-transport and specific heat behavior of Cd-doped La _0.5Ca_0.5MnO₃

The temperature-dependent magneto-transport properties and the specific heat of La_0.5(Ca_0.5-xCd_x)MnO₃ (x = 0.0-0.5) are measured for understanding the electronic phase separation behaviors in manganites. It is surprising to observe that Cd-doping enhances the ferromagnetic metallic state and suppresses the insulating state. Two insulator-metal transitions in La_0.5(Ca_0.3Cd _0.2)MnO₃ are observed, one occurs at temperature T _p1 in accordance with the observed paramagnetic-ferromagnetic transition point T_c and the other appears at a lower temperature T_P2. The magnetoresistance of La_0.5(Ca _0.3Cd_0.2)MnO₃ as a function of temperature shows a sharp peak around T_C, and remains roughly unchanged over a wide temperature range below T_P1. It is argued that these fantastic properties are attributed to the coexistence of ferromagnetic metallic state and ferromagnetic insulating state under an antiferromagnetic background due to the Cd-doping effect.