High Coercive Thin Films of Co-Doped γ-Fe₂O₃–Fe₃O₄ Solid Solution

Abstract

Fe 3+ [Fe 3+ 1+2δ Fe 2+ 1-3δ Δ δ ]O 4 thin films have been prepared by oxidizing sputter-deposited magnetite, where Δ and δ indicate the vacancy and its content, respectively. The coercive force, H c , exhibited the maximum value when δ was approximately 0.20. Films with a δ of more than 0.18 had only an infinitesimal H c increase even after 6 years of aging at room temperature. It was surmised that enhanced Fe 2+ - Δ ordering stabilizes the H c change with time. (Co 0.023 Fe 0.977 ) 2.80 Δ 0.20 O 4 films had a 1300 Oe H c and 0.85 squareness ratio. These films are thought to be useful for high bit density magnetic disk application.