Invesigation on Mesoscopic Ferromagnetic Metals by Using Single Electron Transistor

利用单电子晶体管研究介观铁磁金属

• 批准号: 10640331
• 负责人: SHIMADA Hiroshi
• 金额: $ 2.37万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640331/
• 关键词: single electron transistor; ferromagnetic metal; charging effect; mesoscopic; magneto-Coulomb oscillation; tunneling; 強磁性; 帯電効果

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.

在这个项目中，我们研究了铁磁单电子晶体管（FSET）在磁场中的行为。铁磁单电子晶体管是指其电极部分由铁磁金属制成的单电子晶体管，在这样的系统中，我们发现了在外加磁场中几乎周期性的电导振荡，我们称之为磁库仑振荡（MCO振荡）。这是这个项目的起点。在本项目中，我们特别从实验和理论两个角度阐明了MCO的机理。我们还探索了这种现象作为研究铁磁金属电子结构的工具以及作为FSE器件功能操作的基础的可能应用。在该模型中，磁场诱导电导振荡的起源在于塞曼效应和铁磁金属中价电子的自旋极化。这两个因素在磁场中引起铁磁金属的化学势的变化，就像在通常的单电子晶体管中通过栅极电势一样。我们对Ni/Co/Ni，Co/Ni/Co，Al/Co/Al，Al/Al/Al，Al/Ni/Al和Ni/Al/Ni FSET的实验研究表明，该模型与该模型具有半定量的一致性。通过反过来使用这种现象，我们可以确定铁磁金属的热力学系数（H = H/H）= D2 N = D2，其中H是化学势，H是磁场，N是铁磁体中的电子数。我们已经对Al/Co/Al、Al/Ni/Al和Ni/Al/Ni SET证明了这一点。我们还指出了利用MCO机制和磁化反转的铁磁单电子器件作为磁场驱动功能器件的可能操作。

项目成果

Keiji Ono: "Ferromagnetic Single Electron Transistor" Solid-State Electronics. 42・7-8. 1407-1411 (1998)

小野敬二：“铁磁单电子晶体管”固态电子学42・7-8（1998）。

H. Shimada et al.: "Magneto-Coulomb Oscillation in Ferromagnetic Single Electron Transistors"J. Phys. Soc. Jpn.. 67. 1359-1370 (1998)

H. Shimada 等人：“铁磁单电子晶体管中的磁库仑振荡”J。

K. Ono et al.: "Ferromagnetic Single Electron Transistor"Solid-State Electron. 42. 1407-1411 (1998)

K. Ono 等人：“铁磁单电子晶体管”固态电子。

K. Ono, et al.: "Ferromagnetic Single Electron Transistor"Solid-State Electronics. 42. 1407-1411 (1998)

K. Ono 等人：“铁磁单电子晶体管”固态电子学。

Keiji Ono: "Spin Polarization and Magneto-Coulomb Oscillations in Ferromagnetic Single Electron Devices" Journal of the Physical Society of Japan. 67・8. 2852-2856 (1998)

小野敬二：“铁磁单电子器件中的自旋极化和磁库仑振荡”，日本物理学会杂志 67・8（1998 年）。