Strong Enhancement of Room Temperature Ferrimagnetism in Insulating CoFe₂O₄ by Site-Specific Hydrogen Intercalation.

Abstract

Strong enhancement of magnetization is highly desirable for increasing device efficiency, improving temperature stability, enhancing sensitivity, and enabling device miniaturization. Here, we demonstrate a 2.6-4.7 times higher room temperature ferrimagnetic moment (730-770 emu cc^-1) compared to 170-260 emu cc^-1 in as-grown CoFe₂O₄ films, achieved by site-specifically intercalating hydrogen ions near the Fe³⁺ in tetrahedral sites. While the spin moments of the Fe³ ⁺ at octahedral and tetrahedral sites cancel each other out in as-grown films, X-ray spectroscopy of hydrogenated films reveals that both Fe³⁺ and Co²⁺ at octahedral sites can contribute to the enhanced total magnetic moment. This robust enhancement in insulating CoFe₂O₄, exhibiting high reproducibility over ≈10 cycles and long-term stability over ≈10 d, suggests that hydrogenic-ferrimagnetic coupling holds great promise for ultralow power electronics operating at high frequencies.