Magnetic and Transport Properties of Electron-Doped BaCoS2: Coexistence of Antiferromagnetism and Metallic Conductivity

The layered compounds Ba 1- x Bi x CoS 2 (0≤ x ≤0.7) were prepared in a single phase of the BaCoS 2 type. The electric resistivity was found to be drastically decreased with x and shows a systematic change from insulating to metallic with decreasing temperatures: the electric resistivity for x ≥0.05 follows the T 2 -dependence below 20 K, indicating that the Fermi liquid state is realized at low temperatures, while it shows semiconducting temperature dependence at high temperatures. The electronic specific heat coefficient γ for Ba 0.95 Bi 0.05 CoS 2 was estimated to be a small value of 3.5 mJ/mol·K 2 instead of the large T 2 -term in the resistivity. In magnetic susceptibility measurements, the antiferromagnetic ordering was found to be stable even in metallic samples. These results can be understood as: two types of electronic bands near the Fermi level in the electron-doped BaCoS 2 , one of which has the Mott-Hubbard gap giving rise to the antiferromagnetic ordering just as BaCoS 2 and the other has a ...