Invesigation on Mesoscopic Ferromagnetic Metals by Using Single Electron Transistor

在这个项目中，我们在磁场中研究了铁磁单电子晶体管（FSET's）的行为。在术语“铁磁单电子晶体管”中，我们是指单电子晶体管的组成部分是由铁磁金属制成的，在这样的系统中，我们发现了应用磁场中的大多数周期振荡，我们称之为“磁耦合振荡（MCO）”。这就是这个项目的起点。在这个项目中，我们从两个实验和理论观点的理论角度详细地阐明了MCO的机制。我们还将此phenomenon作为一个工具到investigate the electronic structure of ferromagnetic metals and作为FSE devices的功能操作的基础。我们还将构建一个模型到elucidate the phenomenon of MCO。在Zeemann效应中的磁场诱导的行为振荡效应的起源模型中，以及铁磁金属中的Valence电子的自旋极化。这两个因素导致了电磁场中电磁金属的化学潜力的变化，只是在一种相同的方式，而在普通非磁性装置中的门潜力。我们对Ni/Co/Ni、Co/Ni/Co、Al/Co/Al、Al/Al/Al、Al/Ni/Al和Ni/Al/Ni FSET的模型进行了实验，并找到了与该模型的半定量一致性。通过使用这个现象转换，我们可以确定铁磁金属（κ β/κ H）的热同步系数，其中β是化学潜力， H代表磁场，N是铁磁网中的电子数目。我们为Al/Co/Al、Al/Ni/Al和Ni/Al/Ni SET演示了这一点。我们还确定了铁磁单电子器件的可能操作，作为磁场驱动的功能器件，使MCO机制和磁化反向有效。

In this project we have investigated the behavior of ferromagnetic single electron transistors (FSET's) in a magnetic field. With the term 'ferromagnetic single electron transistor' we mean a single electron transistor part of whose electrode is made of ferromagnetic metals, and in such a system we discovered a conductance oscillation almost periodic in applied magnetic field, which we call 'magneto-Coulomb oscillation (MCO)'. That was the start point of this project. In this project, we have especially clarified the mechanism of MCO from both experimental and theoretical point of view. We have also explored the possible application of this phenomenon as a tool to investigate the electronic structure of ferromagnetic metals and as a basis for functional operations of FSE devices.We have constructed a model to elucidate the phenomenon of MCO. In the model the origin of the magnetic-field induced conductance oscillation consists in the Zeemann effect and the spin polarization of the valence electrons in ferromagnetic metals. These two factors induce a change in chemical potential of the ferromagnetic metal in a magnetic field, just in a same way as by a gate potential in usual nonmagnetic SET's. We experimentally examined this model for Ni/Co/Ni, Co/Ni/Co, Al/Co/Al, Al/Al/Al, Al/Ni/Al and Ni/Al/Ni FSET's, and have found semi-quantitative consistency with the model. By using this phenomenon conversely, we can determine a thermodynamic coefficient of a ferromagnetic metal (∂ζ/∂H)ィイD2NィエD2, where ζ is the chemical potential, H means the magnetic field and N is the number of electrons in the ferromagnet. We have demonstrated this for Al/Co/Al, Al/Ni/Al and Ni/Al/Ni SET's. We have also indicated a possible operation of ferromagnetic single electron devices as magnetic-field driven functional devices utilizing MCO mechanism and magnetization reversal.