A unique high-magnetization iron oxide in metal/native oxide multilayers

Recently, magnetically soft, high-resistivity thin films have been fabricated using a metal/native oxide multilayer (MNOM) structure [1]. Here, a study of the magnetic properties of the native oxide in the model Fe MNOM system is presented. The native oxide, formed from 8.5Åof iron, has a magnetization exceeding that of (Fe_3O_4) by 42%, giving it the highest magnetization of any known iron oxide. The magnetization arises from only a fraction (70%) of the oxide whose spins contribute a net moment of 2.0(1) μ_B/Fe ion, which is ferromagnetically coupled to the metal. This component has an estimated Curie temperature near that of metallic Fe. The remaining iron oxide spins show zero net moment and a strongly temperature dependent atomic moment. The characteristics and implications of this new high-magnetization native iron oxide phase will be discussed. [1]G.S.D. Beach, et.al., Appl. Phys. Lett. 79, 224 (2001)