@article{SisLab1280,
          volume = {50},
           title = {Electrical and Magnetotransport Properties of La0.7Ca0.3Mn1?xCoxO3},
          author = {Dang Thanh Tran and T. L Phan and Quoc Thanh Phung and Nam-Nhat Hoang and Anh Tuan Duong and S. C Yu},
            year = {2014},
           pages = {2502404},
         journal = {IEEE Transactions on Magnetics},
             url = {https://eprints.uet.vnu.edu.vn/eprints/id/eprint/1280/},
        abstract = {This paper presents a detailed study on the Co-doping influence on the electrical and magnetotransport properties of La0.7Ca0.3Mn1-xCoxO3(x = 0.09-0.17) prepared by solid-state reaction. Magnetic measurements versus temperature revealed a gradual decrease of the magnetization (M) and Curie temperature (T-C) with increasing Co concentration (x). The T-C values vary from 194 to 159 K as changing x from 0.09 to 0.17, respectively. H/M versus M-2 performances around T-C prove the x = 0.09 sample undergoing a first-order magnetic phase transition (FOMT) while the samples with x {\ensuremath{>}}= 0.11 undergo a second-order magnetic phase transition (SOMT). The other with x = 0.10 is considered as a threshold concentration of the FOMT-SOMT transformation. Considering temperature dependences of resistivity, rho(T), in the presence and absence of the magnetic field, the samples (excepting for x = 0.17) exhibit a metal-insulator transition at T (P) = 60-160 K, which shifts toward lower temperatures with increasing x. In the metallic-ferromagnetic region, the rho(T) data are well fitted to a power function rho(T) = rho(0) + rho(2) T-2 + rho(4.5) T-4.5. This indicates electron-electron and electron-magnon scattering processes are dominant at temperatures T {\ensuremath{<}} T (P). In addition, the conduction data at temperatures T {\ensuremath{>}} theta(D)/2 (theta(D) is the Debye temperature) and T (P) {\ensuremath{<}} T {\ensuremath{<}} theta(D)/2 obey the small-polaron and variable-range hopping models, respectively. The values of activation energy E-p, and density of states at the Fermi level N(E-F) were accordingly determined. Here, N(E-F) increases while E-p decreases when an external magnetic field is applied. We also have found that N(E-F) increases when materials transfer from the FOMT to the SOMT, and N(E-F) value becomes smallest for the sample having the coexistence of the FOMT and SOMT (i.e., x = 0.10).}
}