ε-iron oxide exhibiting high-frequency millimeter wave absorption

Abstract

This review article describes the large coercive field and high frequency millimeter wave absorption of ε-Fe2O3. In 2004, we obtained pure ε-Fe2O3 phase by a particular chemical synthesis method for nanosize particles, a combination method of reverse-micelle and sol-gel techniques. This ε-Fe2O3 exhibits a huge coercive field of 20 kOe at room temperature. In addition, its physical properties can be widely controlled by substituting the iron cations with other metal cations. In this paper, the synthesis, crystal structure, magnetic properties, and especially, the millimeter wave absorption properties of ε-Fe2O3 and metal substituted ε-Fe2O3, ε-MxFe2-xO3 (M = Al and Ga) are presented. ε-Fe2O3 and ε-MxFe2-xO3 based magnets have the possibility as millimeter wave absorbers for the future high-speed wireless communications.