Preparation and physical properties of the solid solutions Cu 1+xMn 1-xO 2 ( 0⩽x⩽0.2)

Solid solutions of formula Cu _1+xMn _1-xO ₂ ( 0⩽x⩽0.2) were synthesized by solid state reaction in silica sealed tubes. They crystallize with the monoclinic crednerite structure (space group C2/ m). The stability domain in air is quite narrow and a phase diagram is proposed and compared with previous results. Magnetic study confirmed the HS state of Mn ³⁺ ions and revealed that the predominant interactions are antiferromagnetic. Their strength decreases with x, which can be ascribed to a dilution effect, and long-range 3D magnetic ordering observed for CuMnO ₂, disappears for x> 0.05. The crednerite solid solutions are p-type semiconductors. Modeling the thermoelectric power behavior suggests that charge carriers are Cu ²⁺ holes diffusing in Cu layers for small x values and Mn ⁴⁺ holes diffusing in Mn layers for x>0.05. For larger x values a saturation effect limits the charge carrier concentration.