Fabrication of magnetic metal wires by using self-organization on stepped surfaces and its application to three dimensional super lattices

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It is well known that metallic superlattices with artificial one-dimensional periodicity show important properties such as interlayer exchange coupling, magnetoresistance and perpendicular magnetic anisotropy. Giant magnetoresistnace is actually used for reading heads of high density magnetic recording systems. However, the method of multilayering is limited to preparation of one-dimensional periodic structures. It is hoped that a new method to fabricate artificial periodic structures, which could be applied for three-dimensional artificial nanostructures, is developed.In this study, we have studied structures and magnetic properties of magnetic metal wires and films grown at step edges of nonmagnetic underlayers. Additionally, we have investigated on possibility that such a self-organization process is utilized for forming and controlling three dimensional nanostructures. The main result of this study is structural control and enhanced coercivity in FePt alloy films grown on stepped Pt underlayers. The enhanced coercivity is an useful effect, and is explained by domain wall pinning at step edges. For the enhanced coercivity, geometrical effects play an significant role, and the coercivity depends not only on the miscut angle but also the miscut direction of substrates. Results for basic understandings of thin film growth and self-organization process are also obtained. Monatomic layer control is achieved in Co/Ru system, and artificial antiferromagnetic CoRu alloys are prepared. Low-temperature fabrication of L1_0-ordered FePt alloys is successfully performed by the same technique.