PNNL

Abstract

Magnetic spinel oxides have attracted extensive research interest due to their rich physics and wide range of applications. However, these materials invariably suffer suppressed magnetization, due to structural imperfections (e.g., disorder and anti-site defects). Here, we obtain a dramatic enhanced magnetization with an increasement of 5 µB/u.c in CoFe2O4 through ionic liquid gating induced hydrogen doping. The intercalated hydrogen ions lead to both distinct lattice expansion of about 0.7% and notable Fe valence state reduction of through electron doping, in which about 17% Fe3+ is reduced into Fe2+. These facts collectively trigger a site-specific spin-flip on tetrahedrally coordinated Co2+ sites that enhances the net ferrimagnetic moment nearly to its theoretical maximum for perfect CoFe2O4.