Magnetic and magneto-resistive properties of Bi-doped (LaCa)MnO3

Bi-doped lanthanum manganites with chemical compositions of BixLa0.67-xCa0.33MnO3 (x = 0, 0.04, 0.1, 0.2) have been prepared by the standard ceramic process. The crystallinity and microstructures of the samples have been investigated by x-ray diffractometry and optical microscopy, respectively. The magnetic and magneto-resistive properties of the samples have been measured by vibrating sample magnetometery and van der Pauw method, respectively, at the temperatures ranging 100 K-300 K with applied magnetic field of 0.4-0.5 T Good crystallinity and high Curie temperature (275 K) have been obtained for the Bi-doped samples with small dosage (x = 0.04, 0.1) even they were sintered at 1200 degreesC, which is about 200 degreesC lower than normal sintering temperature of undoped sample. The Bi-doped samples with the small dosage showed lower relative electrical resistivity and higher magneto-resistive ratio compared to the undoped sample in the most temperatures measured. The Bi-doped samples also exhibited large magneto-resistive ratio (maximum of 15% for x=0.1) at room temperature even under a weak magnetic field of 0.4 T (C) 2000 Kluwer Academic Publishers.