Enhancement of Curie Temperature and Magnetoresistance in thePerovskit es La_2/3Ca_l/3Mn_l-xSi_xO₃

Structural, magnetic, and transport properties of perovskite La_2/3Ca_l/3Mn_l-xSi_xO₃(x = 0, 0.025, 0.05) have been studied. The incorporation of Si decreases the overall resistivity, but obviously increases the Curie temperature (T_C), metal-insulator transition temperature (T_P), and the magnetoresistance ratio MR (defined as R(0) - R(H)/R(0)) near room temperature. Comparing with La_2/3Ca_l/3MnO₃ the T_C , T_P, and MR of the sample with x = 0.05 increase by 30, 45K, and 20%, respectively. Lattice effects may play a more important role than the magnetic dilution in the case of low Si substitution.