Electrical transport and magnetic properties of La2/3Ca1/3MnO3/SiO2 composites

The influence of SiO2 on the electrical transport properties of LCMO/SiO2 composites with different SiO2 contents x is investigated, where LCMO represents La2/3Ca1/3MnO3. Results show that the SiO2 phase not only shifts the metal-insulator transition temperature (Tp) to a high temperature range, but also has an effect on the magnetoresistance (MR) of the composites. The temperature dependence of resistivity indicates that the Tp of the composites is obviously higher than that of pure LCMO, and that the peak resistivity ρmax of the composites is lower than that of pure LCMO. In the SiO2 content x∼0.02, the TP is the highest and ρmax becomes the lowest. The experimental observation is discussed on the basis of the analysis of scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns. Compared with pure LCMO, a possible interpretation is presented by considering the influence of SiO2 on the coupling between ferromagnetic (FM) domains of LCMO