Fabrication of Fe$_{3}$Si/FeSi$_{2}$ Multilayers by Facing Targets Direct-Current Sputtering And The Magnetic Properties

Fe-Si system has various phases such as semiconducting $\beta $-FeSi$_{2}$ and nanocrystalline FeSi$_{2}$, and ferromagnetic Fe$_{3}$Si. An Fe$_{3}$Si/FeSi$_{2}$ multilayer is a new candidate for a ferromagneto/semiconductor heterostructure in spintronics. In order to accumulate the same kind of materials in atomic scale and form a layered structure with sharp interlaces, the interdiffusion of atoms between the layers should be suppressed. Sputtering methods has been applied for a variety of film preparations. Among them, a facing target direct-current sputtering (FTDCS) method has a merit that a film receives less damage during the deposition since a substrate is placed away from plasma. In this study, we employed the FTDCS method and prepared Fe$_{3}$Si (25 {\AA})/FeSi$_{2}$ ($X$ {\AA}) multilayers, wherein the FeSi$_{2}$ layer thickness $X$ was changed between 5 and 20 {\AA}. Their structural and magnetic properties were investigated. The X-ray diffraction measurement indicated that the Fe$_{3}$Si layers are epitaxially grown not only on Si(111) but also up to the top layer across the FeSi$_{2}$ layers. From the magnetization curves measured at room temperature, it was found that the antiferromagnetic and ferromagnetic interlayer couplings are alternatively induced for a change in the FeSi$_{2}$ layer thickness $X$.