Coercivity of γ-(Fe0.74Mn0.15Co0.11)2O3 thin films by dc reactive magnetron sputtering

Thin (Fe0.74Mn0.15Co0.11)3O4 films of 2400 Å were deposited in-situ on Si(111) substrate under well controlled O2 flow rate by dc reactive magnetron sputtering. The coercivity of as-deposited magnetite films is 480–600 Oe. After 360°C, 90 min oxidation process, the films become maghemite γ-(Fe0.74Mn0.15Co0.11)2O3, and the coercivity is increased by a factor of 4–7 to 2300–3500 Oe. The origin of coercivity increment is attributed to magneto-anisotropy arisen from interfacial stress of films and directional order brought by Co and Mn. The magnetostriction of a γ-(Fe0.74Mn0.15Co0.11)2O3 thin film is calculated to be − 12 × 10−6.