Formation and Structure of Iron-Iron Oxide Multilayered Films

Abstract

A superlattice consisting of metallic iron and its oxide could be formed by repeating vacuum depositions of iron at 10^-5 Pa and subsequent surface oxidations at 10^-1 Pa. Bragg peaks due to the metal-oxide stacking periodicity were observed which indicated that the thickness of the oxide layer was uniform. The magnetization curve and the Mssbauer spectra showed that the thickness of the metal surface oxidized at 10^-1 Pa was almost constant at O.7 nm, irrespective of the thickness of the deposited metal layer, and that the oxide layer consisted of ultrathin layer of Fe₃O₄. When the deposited metallic layer was thicker than 2 nm, a ferromagnetic magnetization curve was observed from the continuous film. However, a superparamagnetic behavior suggesting formation of island-like fine particles was observed when the thickness was 1 nm.