Giant Coercive Field of Nanometer‐ Sized Iron Oxide

Nanocrystals of iron oxide in a silica matrix exhibiting a giant H c value of 2.0 T at room temperature are reported. The nanocomposite was obtained by combining reverse‐micelle and sol–gel methods. The nanocrystals of iron oxide are composed of the ϵ‐Fe 2 O 3 phase, with rod‐like particles 100–140 nm long and 20–40 nm wide. The Figure shows the hysteresis curve of the nanocrystals.