Effects of Mn substitution on the structure and properties of chalcopyrite-type CuInSe2

Mn-doped CuInSe2 compounds (CuIn1−xMnxSe2, x=0.0125–0.20 and Cu1−yIn1−yMn2ySe2, 2y=0.0125–0.60) were synthesized by high-temperature solid-state reactions. Single phase materials with chalcopyrite structure persist up to 0.10 and 0.20 doping for CuIn1−xMnxSe2 and Cu1−yIn1−yMn2ySe2, respectively. The chalcopyrite and sphalerite phases co-exist in the Cu1−yIn1−yMn2ySe2 system for 2y=0.25–0.50. Attempts to introduce greater manganese content, x=0.15–0.20 for CuIn1−xMnxSe2 and 2y=0.60 for Cu1−yIn1−yMn2ySe2, result in partial phase segregation. For the single-phase samples, the lattice parameters of both systems increase linearly with manganese concentration and thus follow Vegard's law. The temperature of the chalcopyrite–sphalerite phase transition is decreased by manganese substitution for all single-phase samples. The bandgap of the materials remains around 0.9 eV. Additionally, the Mn-doped CuInSe2 compounds display paramagnetic behavior, whereas pure CuInSe2 is diamagnetic at 5–300 K. All the CuIn1−xMnxSe2 and Cu1−yIn1−yMn2ySe2 compounds with chalcopyrite structure show antiferromagnetic coupling and measured effective magnetic moments up to 5.8 μB/Mn.