Structural, Optical and Magnetic Characterization of Monodisperse Transition Metal-Doped ZnO Nanocrystals for Potential Spintronics Applications

We present here our results on the synthesis and characterization of transition metal (TM) doped-ZnO nanocrystals, where (TM= Co, Ni, Fe, Cu and Cr). Stable suspensions of these materials were produced in ethanol solution at room-temperature condition. liquors. XRD characterization of doped systems confirmed the exclusive formation of the host ZnO wurtzite structure. The incorporation of dopant species was also confirmed by ICP quantitative analyses of produced powders. The kinetics of the oxide forming reaction was affected by the presence of dopant species; the presence of Ni ions in starting solutions delayed the formation of the oxide. UV-visible and photoluminescence (PL) measurements confirmed not only the nanocrystalline nature of the samples but also evidenced the continuous growth of the crystals when aged in their mother liquors. Room-temperature SQUID measurements indicated that the ferromagnetic or paramagnetic behavior of doped ZnO was dependent on composition and crystal size of produced nanocrystals. A weak but evident room-temperature ferromagnetism was established in the Ni-,(x=0.02, aged for 6 days),and Cu-doped ZnO (x=0.05, aged for 24 hours)nanocrystals.