Transport and Magnetic Properties of K0.8Fe2−x Cu x Se2(0 ⩽ x ⩽ 2) System

We have grown a series of high-quality single crystals of K0.8Fe2−x Cu x Se2(0 ⩽ x ⩽ 2) by Bridgman method and investigated their physical properties by measurements of X-ray diffraction, electrical resistivity, and magnetic susceptibility. The elemental composition analysis shows that it is easy to incorporate Cu dopants. The electrical conductivity and dc magnetic susceptibility measurements show that these doped samples are semiconductors with spin glass behavior at low temperature. The activation energy has a similar trend to the entropy of mixing for two kinds of atoms in the lattice which suggests the semiconducting and spin glass behavior that may be caused by the the random distribution of Fe and Cu ions in the Fe/Cu plane.