Sizeable magnetic circular dichroism of artificially precipitated Co clusters in amorphous carbon

This study examines sizeable magnetic circular dichroism (MCD) in Co(20%)-doped amorphous carbon (a-C) films. While as-grown films exhibit a non-detectable MCD signal, films that undergo rapid thermal annealing (RTA) at 600°C in a vacuum yield broad MCD spectra with a large amplitude of ∼3.9 × 104 deg/cm in saturation field 0.78 T at the σ-σ* gap transition (∼5.5 eV). In such films after RTA, the metastable Co-C bonding is decomposed and suitable Co nanoparticles/a-C interfaces are thus formed. Our results indicate that the large change in MCD is contributed from Co nanoparticles and associated with the spin-dependent electronic structure at the Co/a-C interfaces.