Migration Path and Charge Conversion of Cation in Co-Substituted Spinel Ferrite Thin Film During Magnetic Annealing

Abstract

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 measured as a function of magnetic annealing time. Changes in Mossbauer and X-ray photoelectron spectroscopic (XPS) spectra were also measured. For Go-substituted ferrite thin films, peaks were observed in the plots of the coercivity and lattice parameter vs annealing time, while those for Go-free ferrite thin films were nearly constant during magnetic annealing. From subsequent Mossbauer and XPS experiments, it was confirmed that the peaks in the coercivity and lattice parameter vs annealing time curves for Go-substituted ferrite thin films originate from the migration of Co ions on octahedral sites (B sites) to tetrahedral sites (A sites) and Fe ions on the A sites to the B sites. It is also suggested that the charge valencies of Co ions on the B sites change from +2 to +3 when they reach the A sites, and return to +2 when they arrive at the B sites.