Study on the Tunneling Effect into Amorphous Magnetic Alloys

Research Project

Project/Area Number	61540226
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	固体物性
Research Institution	Yokohama National University
Principal Investigator	SUEZAWA Yoshitaka Yokohama National University, Faculty of Engineering (Assistant Professor), 工学部, 助教授 (30143738)
Co-Investigator(Kenkyū-buntansha)	KAKUNO Keiichi Yokohama National University, Faculty of Engineering (Professor), 工学部, 教授 (40017918) GONDO Yasuo Yokohama National University, Faculty of Engineering (Professor), 工学部, 教授 (50017852)
Project Period (FY)	1986 – 1987
Project Status	Completed (Fiscal Year 1987)
Budget Amount *help	¥1,600,000 (Direct Cost: ¥1,600,000) Fiscal Year 1987: ¥400,000 (Direct Cost: ¥400,000) Fiscal Year 1986: ¥1,200,000 (Direct Cost: ¥1,200,000)
Keywords	Ferro magnetic metals / Amorphous / Thin film / Spin polarized tunneling effect / 電子状態 / 磁性 / トンネル効果
Research Abstract	Dependence on the spin directions is an interesting factor determining the tunneling current between the two metals seperated by a thin layer of insulator. The purpose of the present research project is to acquire the basic understanding of magnetic properties of magnetic alloys, especially of amorphous magnetic alloys, by means of the spin polarized tunneling spectroscopy, in which the sharpe edges at the energy gap of a superconducting Al electrode are usually used as s "probe" to investigate spin-polarized energy states in the conter electrode. The current versus applied voltage curves (I-V)curves of tunnel junctions were measured in temperatures between 1 K and 300 K, and in magnetic fields less than 15 kOe. The lock-in amplifier was adopted to the electronic system to enable measurements of di/dV characteristics. A thin layer of Al of more than 50 A thickness was vaccum evaporated onto a magnetic metal electrode under investigation, and was then oxidized in air to form a tunnel barrier of Al_2O_3, on which the counter electrode of known electronic state was finally vaccum evaporated. The structure of tunnel junctions prepared in the present study was Glass substrate/Magnetic metal/Al_2O_3/ Metal of the known electronic state, whic is different form the usual structure of Al/Al_2O_3/Magnetic metal. The present structure enables the investigation of lectron tunneling into various metals, since the very thin Al_<23> layer is not damaged during the formation of the magnetic metal films. NiO tunnel barrier formed on a Ni electrode by means of oxidation in air was also investigated. The tunnel effects of Ni/NiO/Ni and Ni/NiO/Co junctions were investigated, and a new type of magneto-resistance effect was found. The application of the spin polarized tunneling effect is being extended into the study of the magnetism of amorphous alloy films, whose various magnetic and structural measurements have been made.