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Study of tunnel transport and novel giant magnetoresistance effect in metal-nonmetal granular alloys

金属-非金属颗粒合金隧道输运及新型巨磁阻效应研究

基本信息

批准号：
07405030
负责人：
FUJIMORI Hiroyashu
金额：
$ 20.42万
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：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

Metal-nonmetal granular alloy thin films consist of magnetic metal granules and insulating matrix, and they exhibit a novel giant magnetoresistance due to spin dependent tunneling. In this research project, we have investigated mechanism of the tunnel-type giant magnetoresistance in metal-nonmetal granular alloy thin films in order to understand (i) the general aspect of tunneling magnetoresistance and (ii) magnetotransport phenomena in microscopic magnetic materials. In addition, we have attempted to apply this tunnel-type giant magnetoresistance to practical magnetic sensing devices.Metal-nonmetal granular alloy thin films of Co-Al-O etc.were prepared by reactive sputtering. Microstructural analysis and magnetic and transport measurement were performed for the films. From these results, it is understood that the basic mechanism of the magnetoresistance is the same as that of ferromagnetic tunnel junctions. However, anomalous enhancement of magnetoresistance at low temperatures and an … More omalous bias voltage dependence of resistivity and magnetoresistance have also found for the granular alloy films. For example, the magnetoresistance value of Fe-Al-O films reaches more than 30% at 4.2K.From systematic measurements of magnetoresistance, we conclude that the anomalous behavior is attributed to a higher-order tunneling effect to which a charging effect of nanometer-sized granules gives rise. The charging effect is characteristic for granular systems and is quite interesting in the research field of magnetotransport and its application. The enhanced magnetoresistance observed in this research may be used for magnetic sensors with large magnetoresistive response.In addition to above results, we have succeeded in improvement of the field sensitivity of magnetoresistance of metal-nonmetal granular alloy thin films. As metal-nonmetal granular alloy films were hybridized with soft magnetic alloy film possessing a lateral gap (we call it Granular-In-Gap structure), the effective magnetic field applying metal-nonmetal granular alloy was enforced and large magnetoresistance appeared at very low external magnetic field. In the case of permalloy used for soft magnetic alloy, only a few Oe of external field is required to obtain a large magnetoresistive response. This hybrid structure containing metal-nonmetal granular alloy is considered to be useful for practical applocations of magnetic sensing materials Less

金属-非金属颗粒合金薄膜由磁性金属颗粒和绝缘基体组成，由于自旋相关隧穿效应而表现出一种新型的巨磁电阻效应。在本研究计划中，我们研究了金属-非金属颗粒合金薄膜中隧道型巨磁电阻的机制，以了解（i）隧道磁电阻的一般情况和（ii）微观磁性材料中的磁输运现象。此外，我们还尝试将这种隧道型巨磁电阻效应应用于实际的磁敏器件中，用反应溅射法制备了Co-Al-O等金属-非金属颗粒合金薄膜。对薄膜进行了微结构分析、磁性和输运测量。从这些结果可以看出，磁电阻的基本机制与铁磁隧道结相同。然而，在低温下磁电阻的异常增强和 ...更多信息对于颗粒状合金膜，还发现电阻率和磁阻的反常偏压依赖性。例如，Fe-Al-O薄膜在4.2K时的磁电阻值达到30%以上。通过系统的磁电阻测量，我们认为这种反常行为是由纳米颗粒的充电效应引起的高阶隧穿效应引起的。荷电效应是颗粒系统的一个重要特征，是磁输运及其应用研究领域的一个热点。本研究中所观察到的增强的磁阻效应可用于具有大磁阻响应的磁传感器。除上述结果外，我们还成功地提高了金属-非金属颗粒合金薄膜的磁阻场灵敏度。由于金属-非金属颗粒合金薄膜与具有横向间隙的软磁合金薄膜杂化（我们称之为Granular-In-Gap结构），金属-非金属颗粒合金施加的有效磁场增强，在很低的外磁场下就出现了大的磁电阻。在坡莫合金用于软磁合金的情况下，仅需要几个Oe的外场就可以获得大的磁阻响应。这种含有金属-非金属颗粒合金的混合结构被认为对磁敏感材料的实际应用是有用的。