We report the electronic properties of the layered bismuth-based sulfide superconductors NdO 1−x F x BiS 2 (x = 0.25, 0.4, and 0.5) and La 1−y Sm y O 0.5 F 0.5 BiS 2 (y = 0.1 -0.7), which have been studied by investigation of their transport properties and X-ray diffraction. In the lightly carrier-doped NdO 1−x F x BiS 2 (x = 0.25 and 0.4) and La 1−y Sm y O 0.5 F 0.5 BiS 2 (y = 0.3 and 0.4), the resistivity and Hall coefficient exhibit anomalous temperature dependences below T CDW ∼ 130 and 200 K, respectively, suggesting the formation of an energy gap on the Fermi surface associated with charge-density wave (CDW). In NdO 1−x F x BiS 2 (x = 0.25), the bond angles and bond length of the Bi-S pentahedron change their temperature dependences below ∼ 200 K, suggesting that a lattice instability related to the Bi-S pentahedron exists below ∼ 200 K, which is much higher than T CDW . These results indicate that the lattice instability of the Bi-S pentahedron can trigger a CDW transition in the low-carrier region of BiS 2 superconductors.

Hagi ware originally consists of a mixture of two raw materials: Daido clay and Mishima clay. During its firing process, we observed a change in the magnetic properties of the iron oxide, Fe 2 O 3 . The magnetic moment of the Daido clay (which only contains a small amount of the Fe 2 O 3 £-phase) attains a maximum at a firing temperature of approximately 600°C, where a minor amount of the poorly crystallized Fe 2 O 3 temporarily changes to the ferromagnetic £-phase. Furthermore, the magnetic moment of the Mishima clay (which contains a large amount of the Fe 2 O 3 £-phase) decreases as the firing temperature increases, whereas the coercive field rapidly increases at firing temperatures above 1000°C. The magnetization curve of the Mishima clay that was fired at temperatures above 1200°C is characteristic of a two-component system consisting of a minor £-phase and a major ¡-phase. The above-mentioned phenomena were also confirmed by XRD analyses. A series of experiments indicated that the firing of Hagi ware can be characterized as a transformation from the £-phase of Fe 2 O 3 to the ¡-phase of Fe 2 O 3 . This transformation is considered to contribute to the change from soft magnetism to hard magnetism of Hagi ware.