The Cation Distributions of Zn-doped Normal Spinel MgFeO Ferrite and Its Magnetic Properties.

Determining the exact occupation sites of the doping ions in spinel ferrites is vital for tailoring and improving their magnetic properties. In this study, the distribution and occupation sites of cations in MgFeO and Zn-doped MgFeO ferrite are imaged by Cs-STEM. The experimental STEM images along [001], [011] and [111] orientations suggest that the divalent Mg cations occupy all A sites, and the trivalent Fe cations occupy all B sites in MgFeO ferrite prepared by electrospinning, which is consistent with the normal spinel structure. We further clarify that the preferred sites of dopant Zn ions are Fe crystallographic sites in the Zn-doped MgFeO ferrite nanofibers. Magnetic measurements show that Zn doping affects the spin states of the Fe, and the Fe-O-Fe super-exchange interaction leads to enhancements in the magnetization and reduction in the Curie temperature. Our work should contribute a significant step toward eventually realizing the practical application of doped spinel ferrites.