MIGRATION PATH AND CHARGE CONVERSION OF CATIONS IN CO-SUBSTITUTED SPINEL FERRITE THIN-FILMS DURING MAGNETIC ANNEALING

The migration path and charge conversion of cations in Go-substituted spinel ferrite thin films during magnetic annealing are investigated. To this end, changes in the coercivity and lattice parameter were meas ured as a function of magnetic annealing time. Changes in Mossbauer an d X-ray photoelectron spectroscopic (XPS) spectra were also measured. For Go-substituted ferrite thin films, peaks were observed in the plot s of the coercivity and lattice parameter vs annealing time, while tho se for Go-free ferrite thin films were nearly constant during magnetic annealing. From subsequent Mossbauer and XPS experiments, it was conf irmed that the peaks in the coercivity and lattice parameter vs anneal ing time curves for Go-substituted ferrite thin films originate from t he migration of Co ions on octahedral sites (B sites) to tetrahedral s ites (A sites) and Fe ions on the A sites to the B sites. It is also s uggested that the charge valencies of Co ions on the B sites change fr om +2 to +3 when they reach the A sites, and return to +2 when they ar rive at the B sites.