Room-Temperature Ferromagnetism in Mn-Doped CuCrO<sub>2</sub> Nanopowders

(Cu1-xMnx)CrO2 (0≤ x ≤6 at%) and Cu (Cr1-yMny)O2 (0≤ y ≤6 at%) nanopowders were prepared by combining solid-state reaction and ball milling. The Mn concentration dependences of microstructure, morphology and magnetic properties were investigated. It is found that all the samples have a pure 3R-CuCrO2 delafossite structure. The lattice expansion supports the Mn entrance into the Cu and Cr sublattices, respectively, in (Cu1-xMnx)CrO2 and Cu (Cr1-yMny)O2, which is further proved by X-ray photoelectron spectroscopy to some degree. A-site Mn substitution brings about paramagnetic behavior. However, room-temperature ferromagnetism is achieved in B-site Mn-doped samples, originating from the hole-mediated Cr3+–Mn3+ double-exchange interaction. The saturation magnetization of this CuMO2 delafossite (M=Cr, Mn) is about an order of magnitude higher than literature values, and gradually decreased with the Mn addition due to the combined influence of the number of the M–M pairs, the M–M distances and the hole density.