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

Mn-doped CuInSe₂ compounds (CuIn_1−xMn_xSe₂, x=0.0125–0.20 and Cu_1−yIn_1−yMn_2ySe₂, 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 CuIn_1−xMn_xSe₂ and Cu_1−yIn_1−yMn_2ySe₂, respectively. The chalcopyrite and sphalerite phases co-exist in the Cu_1−yIn_1−yMn_2ySe₂ system for 2y=0.25–0.50. Attempts to introduce greater manganese content, x=0.15–0.20 for CuIn_1−xMn_xSe₂ and 2y=0.60 for Cu_1−yIn_1−yMn_2ySe₂, 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 CuIn_1−xMn_xSe₂ and Cu_1−yIn_1−yMn_2ySe₂ compounds with chalcopyrite structure show antiferromagnetic coupling and measured effective magnetic moments up to 5.8 μ_B/Mn.