Robust ferromagnetism in rare-earth and transition metal co-doped ZnO nanoparticles for spintronics applications

•Co-precipitation derived single-phase (Tb,Co) co-doped NPs exhibit strong RTFM.•No secondary phase or cluster was detected by XRD and TEM analysis.•XPS and PL study confirm the presence of oxygen vacancies in prepared samples.•The magnetization value is sensitive to the oxygen vacancies.•The observed RTFM emerge from oxygen vacancies mediated bound magnetic polarons. This work reports on the robust ferromagnetism at room temperature in co-precipitation derived rare-earth (Tb) and transition metal (Co) co-doped ZnO nanoparticles (NPs). X-ray diffraction (XRD) analysis reveals the single-phase character. Morphological studies confirm the formation of spherical-shaped particles with different orientations separated by well-defined grain boundaries. The increase in oxygen vacancies is confirmed by photoluminescence (PL) spectra. The (Tb, Co) co-doped NPs exhibit room temperature ferromagnetic (RTFM) behavior, which has been discussed based on oxygen vacancies mediated magnetic polarons and the effect of grain boundaries.