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

众所周知，具有人工一维周期性的金属超晶格具有层间交换耦合、磁电阻和垂直磁各向异性等重要性质。巨磁电阻实际上是用于高密度磁记录系统的读头。然而，多层方法仅限于一维周期结构的制备。希望能开发出一种新的人造周期结构的制备方法，并应用于三维人造纳米结构。在这项研究中，我们研究了生长在非磁性底层阶梯边缘的磁性金属线和薄膜的结构和磁性。此外，我们还研究了这种自组织过程用于形成和控制三维纳米结构的可能性。本研究的主要结果是在阶梯状Pt衬底上生长的FePt合金薄膜的结构控制和矫顽力增强。矫顽力的增强是一种有益的效应，可以用台阶边缘的畴壁钉钉来解释。对于矫顽力的增强，几何效应起着重要的作用，矫顽力不仅与基体的错切角度有关，还与基体的错切方向有关。得到了对薄膜生长和自组织过程的基本认识。在Co/Ru体系中实现了单原子层控制，制备了人工反铁磁CoRu合金。用同样的方法成功地制备了l1_0有序FePt合金。

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.