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

Undoped thin gamma-Fe2O3 films were deposited in-situ on Si substrate under well controlled O-2 partial pressure by dc-reactive magnetron sputtering Fe3O4 phase then controlled oxidation to become the maghemite phase at 360 degrees C for 10 min. The coercivity of as-deposited magnetite films is around 400 similar to 640 Oe. After oxidation at 320-360 degrees C for 10 minutes, the films transform to maghemite gamma-Fe2O3 completely, and the coercivity is increased 1 similar to 4 times to 640 similar to 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.