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Cu(CrMgMn)O ceramics (0 ≤ x ≤ 15 at.%) were prepared by solid-state reaction. The influence of Mg acceptor codoping on microstructure, magnetic, and optical properties was studied. The codoping with Mg acceptors and the resulting lattice expansion are both favorable for the enhancement of hole density. Furthermore, the lower valence of Mg compared with Cr enables the mixed valence state of Mn ions: Mn and Mn, and hence induces the hole-mediated double-exchange mechanism not only between Mn and Cr but also between Mn and Mn. The coexistence of two ferromagnetic interactions and the high hole density are responsible for the improved saturation magnetization and Curie temperature. For photoluminescence, an unusual near-infrared emission at 1.5 eV is observed in the Mn-contained samples and can be attributed to the internal transition between the e and t states of the Mn impurity band. The emission intensity is primarily affected by two factors: the Mn concentration and the position of the Fermi level. The results show that codoping with Mg acceptors is an effective way to strengthen the hole-mediated ferromagnetic interactions in CuCrO delafossite. [ABSTRACT FROM AUTHOR]

Highlights: [•] First study on high-quality Cu(Cr1−xFe x )O2 diluted magnetic semiconductor films. [•] All thin films have a quasi-epitaxial growth orientation along the c axis. [•] Room-temperature ferromagnetism comes from hole-mediated Fe3+–Cr3+ super-exchange. [•] P-type conductivity is enhanced by more than one order of magnitude via Fe doping. [•] All thin films show a comparatively high transparency in the visible range. [ABSTRACT FROM AUTHOR]