Room temperature magnetic ordering and analysis by bound magnetic polaron model of Yb3+ doped nanocrystalline zinc oxide (Zn0.98Yb0.02O)

Nanocrystalline ZnO and Yb-doped ZnO (Zn0.98Yb0.02O) are prepared by simple co-precipitation method. The pure crystallographic phases of ZnO and Zn0.98Yb0.02O are confirmed by Rietveld analyses of XRD patterns. Raman and photoluminescence spectra recorded at room temperature (RT) indicates that lattice defects and oxygen vacancy in Zn0.98Yb0.02O is more than that of ZnO. Magnetic measurements of ZnO and Zn0.98Yb0.02O are carried out from 300 to 5 K. Ferromagnetic ordering is observed in Zn0.98Yb0.02O at RT and the strength of the ordering increases with the lowering of temperature. Ferromagnetism of Zn0.98Yb0.02O is attributed to the oxygen vacancy introduced by annealing in vacuum. Magnetization vs. temperature curve is well fitted by the combination of 3D spin wave and Curie-Weiss law, which suggest simultaneous presence of para- and ferro-magnetic phases in Zn0.98Yb0.02O. Ferromagnetic ordering is successfully explained by vacancy mediated bound-magnetic polaron model.