The Cation Distributions of Zn-doped Normal Spinel MgFe2O4 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 MgFe2O4 and Zn-doped MgFe2O4 ferrite are imaged by Cs-STEM. The experimental STEM images along [001], [011] and [111] orientations suggest that the divalent Mg2+ cations occupy all A sites, and the trivalent Fe3+ cations occupy all B sites in MgFe2O4 ferrite prepared by electrospinning, which is consistent with the normal spinel structure. We further clarify that the preferred sites of dopant Zn2+ ions are Fe3+ crystallographic sites in the Zn-doped MgFe2O4 ferrite nanofibers. Magnetic measurements show that Zn doping affects the spin states of the Fe3+, and the Fe3+-O2--Fe3+ 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.

Automated summary

Determining the occupation sites of doping ions in spinel ferrites is crucial for tailoring their magnetic properties. This study used Cs-STEM to image the distribution and occupation sites of cations in MgFe2O4 and Zn-doped MgFe2O4 ferrite. The results showed that Mg2+ occupied the A sites and Fe3+ occupied the B sites in MgFe2O4 ferrite, while Zn2+ preferred to occupy the Fe3+ crystallographic sites in Zn-doped MgFe2O4 ferrite. Furthermore, Zn doping affected the spin states of Fe3+ and enhanced the magnetization but reduced the Curie temperature. This work is an important step towards practical applications of doped spinel ferrites.