Undoped maghemite thin films with coercivity up to 2100 Oe for magnetic recording

Undoped thin γ-Fe₂O₃ films were deposited in-situ on Si substrate under well controlled O₂ partial pressure by dc-reactive magnetron sputtering Fe₃O₄ phase then controlled oxidation to become the maghemite phase at 360°C for 10 min. The coercivity of as-deposited magnetite films is around 400~640 Oe. After oxidation at 320-360°C for 10 minutes, the films transform to maghemite γ-Fe₂O₃ completely, and the coercivity is increased 1~4 times to 640~2100 Oe, depending on oxygen flow rate during deposition and the thermal history. The origin of coercivity enhancement is attributed to magnetoanisotropy which is induced by the interfacial stress of the films. These films show potential for high density magnetic recording applications due to simplified processing, high coercivity, wear and corrosion resistance