Raman scattering studies in dilute magnetic semiconductor Zn1-xCoxO

Raman spectra of ZnO and Co substituted Zn1-xCoxO (ZCO) were carried out using the Raman microprobe system with an Ar+ ion laser source of 514.5 nm wavelength. The shift towards the lower frequency side of the nonpolar E-2(low) mode and the broadening due to Co substitution in ZnO were analyzed using the phonon confinement model. The magnetic measurements showed ferromagnetic behavior with the maximum saturation magnetization (1.2 mu(B)/Co) for 10% Co substitution, which decreased with at further increase in Co concentrations. The intensities of E-1(LO) at 584 cm(-1) and multiphonon modes at 540 cm(-1) were increased with an increase in Co substitution. The additional Raman modes in ceramic targets of ZCO spectra for higher concentration of Co substitution (x=15%-20%) were identified to be due to the spinel ZnCo2O4 secondary phase.