Development of magnetic tunnel junctions using Heusler alloy and observation of spin-injected magnetization reversal

使用赫斯勒合金开发磁隧道结并观察自旋注入磁化反转

基本信息

批准号：
17206001
负责人：
MIYAZAKI Terunobu
金额：
$ 32.7万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

1. Fabrication of magnetic tunnel junctions using epitaxial Heusler alooy electrodes Large tunnel magneto-resistance (TMR) ratios of 217% at room temperature and 753% at low temperature have been successfully observed in a magnetic tunnel junction (MTJ) using a high quality Heusler alloy electrode and an MgO crystalline barrier. The structure of the MTJ was Co2MnSi/MgO/CoFe. This observed TMR ratio is highest among the MTJs using Heusler alloy electrodes. Moreover, conductance-voltage property of the MTJ investigated in detail indicates that the origin of the large TMR was coherent tunneling process through the crystalline MgO barrier.2. Micro-fabrication of MTJs and Observation of spin-injected magnetization reversal Spin-injected magnetization reversal has been successfully observed in the micro-fabricated CoFeB/MgO/CoFeB-MTJs using (Co_<50>Fe_<50>)_<100-x>B_x (x=20, 25, 30, thickness d=2 nm) switching layers. We found from this result that the switching current density depended on magnetization, damping constant and spin polarization of the ferromagnetic layer as expected by theory and reducing of magnetization and damping constant was quite effective to decrease the switching current density.3. Magnetic damping constant α Magnetic damping constants in various ferromagnetic thin films were investigated systematically by FMR technique. Moreover, a measurement technique for estimation of damping constants in MTJs has been established. As a result, we found that the damping constant of 2nm thick CoFeB film was five times larger than that of bulk CoFeB and the neighboring layer of the switching layer influence the damping constant of the switching layer.

1. 使用外延 Heusler 合金电极制造磁隧道结使用高质量 Heusler 电极在磁隧道结 (MTJ) 中成功观察到室温下 217% 和低温下 753% 的大隧道磁阻 (TMR) 比MTJ 的结构是 Co2MnSi/MgO/CoFe，观察到的 TMR 比率是最高的。使用Heusler合金电极的MTJ的电导-电压特性的详细研究表明，大TMR的起源是穿过晶体MgO势垒的相干隧道过程。2．使用以下方法在微制造的 CoFeB/MgO/CoFeB-MTJ 中成功观察到了自旋注入磁化反转(Co_<50>Fe_<50>)_<100-x>B_x (x=20, 25, 30, 厚度 d=2 nm) 开关层从该结果我们发现，开关电流密度取决于磁化强度、阻尼。铁磁层的常数和自旋极化符合理论预期，降低磁化强度和阻尼常数对于降低开关电流密度非常有效。 3．此外，我们还建立了一种估计 MTJ 阻尼常数的测量技术，结果发现 2nm 厚的 CoFeB 薄膜的阻尼常数比 MTJ 大 5 倍。块状 CoFeB 和切换层的相邻层影响切换层的阻尼常数。