Nuclear magnetic resonance investigations of Co nanoclusters in a SiO2 thin film matrix

Co 59 nuclear magnetic resonance (NMR) spectra of small Co particles in a SiO2 matrix have been measured. In zero field, strong signals were obtained in the frequency range of 210–250 MHz. The Co59 NMR frequency in fcc multi (single) domain particles is 217.4 (223) MHz. Possible contributions to the Co hyperfine field and changes to the Co magnetic moment in nanoclusters are discussed. An enhanced magnetic moment could be responsible for an increase in the hyperfine field leading to the observed NMR line at ∼243 MHz. Measurements of the transverse relaxation time (T2) as a function of temperature and field are reported.