During growth of La 0.67 Ca 0.33 MnO 3 in an usual solid state reaction process, the diffusion of La-site metal ions is a rate-limiting factor. In the initial stage of the growth process, La-deficient manganite with rhombohedral structure was easily formed. With the repetition of the grinding±pressing± sintering process, the metal content on the La-site was gradually increased, and the phase was changed from rhombohedral to cubic structure. For slightly La-deficient (La,Ca) 1Àx MnO 3 manganites, the ferromagnetic±paramagnetic (F±P) transition temperature T M is less sensitive to the Lasite deficiency, but their electric transport properties are greatly affected. The slightly La-site deficient compound was characterized by double bumps on its resistivity versus temperature (R±T) curve, one of which was located at higher temperature very near to its temperature T M . For the La 0.67 Ca 0.33 MnO 3 single phase, only one resistance peak was observed at T R on its R±T curve. For the sample sintered at lower temperatures (< 1100 C) in air T R is much less than T M , and no magnetoresistance (MR) peak was observed within the temperature range of 80 K < T < 300 K. But for the sample sintered at 1200 C in air T R is well in agreement with T M and its MR is strongly peaked very close to T M . All the bulk samples showed substantial MR in a magnetic field of 0.6 T at low temperatures that increased almost linearly with decreasing temperature.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.