Fourfold in-plane magnetic anisotropy of magnetite thin films grown on TiN buffered Si(001) by ion-assisted sputtering

Abstract

Highly oriented magnetite thin films showing well-defined fourfold in-plane magnetic anisotropy have been grown on TiN buffered Si(001) substrates by ion beam sputtering assisted by a second ion beam containing a controlled mixture of Ar⁺ and O₂⁺ ions. The structure and composition of stoichiometric Fe₃O₄ and non-stoichiometric Fe_3−δO₄ magnetite thin films have been characterized by X-ray diffraction, Rutherford backscattering spectroscopy and Mössbauer spectroscopy. Magneto-optical Kerr effect measurements show that the maxima of the remanence and coercivity of all these films lie along the Si[010] and [100] directions. The introduction of Fe vacancies in magnetite does not alter the well-defined fourfold in-plane anisotropy but induces a decrease of the coercive field as the number of vacancies increases. Furthermore, the results indicate that a 5 nm TiN thick buffer layer is enough to maintain the Fe₃O₄[100]/TiN[100]/Si[100] epitaxial relationship.