Demonstration of high-frequency oscillation in a Co-based Heusler alloy tunnel junction

钴基霍斯勒合金隧道结的高频振荡演示

• 批准号: EP/H026126/1
• 负责人: Atsufumi Hirohata
• 金额: $ 9.31万
• 依托单位: University of York
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FH026126%2F1
• 关键词: Demonstration; frequency; oscillation; Co; based

Keywords: half-metals, Heusler alloys, MRAM, Gilbert damping and exchange biasGoals: 1. Establishment of a reproducible process to fabricate a magnetic tunnel junction (MTJ), consisting of a MgO barrier sandwiched with epitaxial Co2FeAl0.5Si0.5 film electrodes.2. Demonstration of very large tunnelling magnetoresistance (TMR) ratio at room temperature (RT).3. Demonstration of efficient current-induced magnetisation switching (CIMS) based on a small Gilbert damping constant and large spin polarisation.4. Nanofabrication of a prototype of a high-frequency spin oscillation with the Co2FeAl0.5Si0.5 junction for the first time.Approach: 1. Device fabrication using ultrahigh vacuum (UHV) sputtering/molecular beam epitaxy (MBE) growth and nanofabrication at NIMS combined with interfacial atomic analysis by state-of-the-art scanning transmission electron microscopy (STEM) at York.2. Based on the above feedback process, nanopillar fabrication of high-quality Co2FeAl0.5Si0.5/MgO/Co2FeAl0.5Si0.5 junctions.3. Highly sensitive magnetisation analysis both at NIMS [current in plane tunnelling analysis and temperature-dependent TMR measuremsnts] and York [vibrating sample magnetometer (VSM) and magneto-optical Kerr effect (MOKE)].4. High-frequency operation of the CIMS in a Heusler-based nanopillar and electrical detection by coplanar waveguide.Expected outcome: 1. To reveal a correlation between atomic structures at the Co2FeAl0.5Si0.5/MgO interfaces and ballistic spin-polarised electron tunnelling properties.2. Improvement of the world-record TMR ratio (386% at RT and 832% at 9 K) and its temperature dependence to follow the empirical temperature dependence of magnetisation.3. Decrease of a critical current density below 106 A/cm24. Estimation of a damping constant of the Co2FeAl0.5Si0.5 film.An intensive search for a new ferromagnetic material with 100% spin polarisation at room temperature has been carried out recently for the realisation of a future spin random access memory application. We will employ Co2FeAl0.5Si0.5 Heusler alloy films, which hold the highest spin polarisation, resulting the largest tunnelling magnetoresistance at room temperature to date. Magnetic tunnel junctions with the Heusler films will be epitaxially grown at the NIMS by ultrahigh vacuum sputtering and molecular-beam epitaxy, and will then be characterised at York with the state-of-the-art electron microscopy and magnetometry. By improving the interfacial atomic structures of the films against a MgO tunnel barrier, larger TMR ratios will be demonstrated. High-frequency measurements will also be performed to define their damping constants, which are to be smaller than the conventional ferromagnets. These junctions are expected to take significant advantages in both ~100% spin polarisation and a very small damping constant for the realisation of fast and efficient switching in a spin memory. At the end of this project, we will attempt to fabricate a prototype of a high-frequency oscillator with Heusler alloy films for the first time.

关键词：半金属，Heusler合金，MRAM，吉尔伯特阻尼和交换偏置目标：1。建立了一种可重复的工艺来制造磁性隧道结（MTJ），该磁性隧道结由MgO阻挡层和外延Co2FeAl0.5Si0.5膜电极组成。在室温（RT）下证明了非常大的隧道磁电阻（TMR）比.基于小的吉尔伯特阻尼常数和大的自旋极化的有效的电流诱导磁化开关（CIMS）的证明.第一次用Co2FeAl0.5Si0.5结制作了一个高频自旋振荡的原型。在NIMS使用超真空（UHV）溅射/分子束外延（MBE）生长和纳米纤维结合约克最先进的扫描透射电子显微镜（STEM）进行界面原子分析来制造器件。基于上述反馈过程，采用纳米柱制备了高质量的Co2FeAl0.5Si0.5/MgO/Co2FeAl0.5Si0.5结.在NIMS [面内电流隧穿分析和随温度变化的TMR测量]和约克[振动样品磁强计（VSM）和磁光克尔效应（MOKE）]进行高灵敏度的磁化分析。在基于Heusler的纳米柱中的CIMS的高频操作和通过共面波导的电检测。揭示Co2FeAl0.5Si0.5/MgO界面原子结构与弹道自旋极化电子隧穿性质之间的相关性.改进了世界纪录的TMR比（RT时为386%，9 K时为832%）及其温度依赖性，以遵循磁化强度的经验温度依赖性。临界电流密度降低到106 A/cm以下4。Co_2FeAl_（0.5）Si_（0.5）薄膜阻尼常数的估算。最近，为了实现未来的自旋随机存取存储器应用，对在室温下具有100%自旋极化的新铁磁材料进行了深入的研究。我们将采用Co2FeAl0.5Si0.5 Heusler合金薄膜，它具有最高的自旋极化，从而在室温下产生最大的隧道磁阻。磁性隧道结与赫斯勒薄膜将外延生长在NIMS的真空溅射和分子束外延，然后将其特征在于在约克与国家的最先进的电子显微镜和磁力。通过改善界面原子结构的膜对MgO隧道势垒，更大的TMR比将被证明。还将进行高频测量以确定其阻尼常数，该阻尼常数小于传统铁磁体。预计这些结在~100%自旋极化和非常小的阻尼常数方面都具有显著的优势，以实现自旋存储器中的快速有效切换。在本计画的最后，我们将首次尝试以Heusler合金薄膜制作高频振荡器的原型。

项目成果

Optimization of exchange bias in Co2FeAl0.5Si0.5 Heusler alloy layers

Co2FeAl0.5Si0.5 Heusler 合金层交换偏压的优化

• DOI: 10.1063/1.4868601
• 发表时间: 2014
• 期刊: Journal of Applied Physics
• 影响因子: 3.2
• 作者: Hirohata A

Heusler-alloy films for spintronic devices

• DOI: 10.1007/s00339-013-7679-2
• 发表时间: 2013-05-01
• 期刊: APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
• 影响因子: 2.7
• 作者: Hirohata, Atsufumi;Sagar, James;Lazarov, Vlado K.
• 通讯作者: Lazarov, Vlado K.

Over 50% reduction in the formation energy of Co-based Heusler alloy films by two-dimensional crystallisation

• DOI: 10.1063/1.4886769
• 发表时间: 2014-07-21
• 期刊: APPLIED PHYSICS LETTERS
• 影响因子: 4
• 作者: Sagar, James;Fleet, Luke R.;Hirohata, Atsufumi
• 通讯作者: Hirohata, Atsufumi

Growth of polycrystalline Heusler alloys for spintronic devices

• DOI: 10.1088/0022-3727/47/26/265002
• 发表时间: 2014-06
• 期刊: Journal of Physics D: Applied Physics
• 作者: J. Sagar;C. Yu;L. Lari;A. Hirohata

POLYCRYSTALLINE CO-BASED FULL-HEUSLER-ALLOY FILMS FOR SPINTRONIC DEVICES

用于自旋电子器件的多晶钴基全霍斯勒合金薄膜

• DOI: 10.1142/s2010324714400219
• 发表时间: 2015
• 期刊: SPIN
• 影响因子: 1.8
• 作者: HIROHATA A