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Controlled spin-polarized electron transport of oxide magnetic semiconductor films of hematite-ilumenite solid solutions by the exchange coupling

交换耦合控制赤铁矿-钛铝矿固溶体氧化物磁性半导体薄膜的自旋极化电子传输

基本信息

批准号：
11650697
负责人：
FUJII Tatsuo
金额：
$ 2.24万
依托单位：
OKAYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Magnetic semiconductors are one of die promising electronics materials for the next generation, so-called spintronics materials. In this research we proposed a novel technique to control the spin-polarized transport of magnetic semiconductors and tried to realize it. The first subject was to develop thin films of new oxide magnetic semiconductors focused on a hematite-ilumenite solid solution system having a high spin polarization at room temperature. There had been many difficulties to prepare well-defined hematite ilumenite solid solution films having good magnetic semiconductive properties, because they had many controllable factors such as an order-disorder transition and Fe^<2+>/Fe^<3+> mixed valence states, etc. We found optimized preparation conditions for the solid solution films by helicon sputtering to control remanent oxygen pressure and substrate temperature precisely. The films showed magnetic semiconductive properties such as magnetoresistance at room temperature. The second subject was to control magnetic structures of ferromagnetic layers by means of a spin-flip transition of antiferromagnetic layers. Only epitaxial hematite films showed a unique spin-flip transition. We prepared hematite/spinel ferrite bilayered films by helicon sputtering and surveyed magnetic properties around the spin-flip transition. The spin-flip transition in a hematite layer disappeared because of a large in-plane magnetic anisotropy of a spinel ferrite layer. We first found the 90° exchange coupling between oxide magnetic layers. Unfortunately we could not realize the proposing spin control technique, but we could obtain huge results concerning preparation techniques for well-defined iron oxide films and their structural, magnetic and electronic properties.

磁性半导体是下一代极具前景的电子材料之一，被称为自旋电子学材料。本研究提出了一种控制磁性半导体自旋极化输运的新技术，并尝试实现它。第一个课题是开发新型氧化物磁性半导体薄膜，重点研究在室温下具有高自旋极化的赤铁矿-褐铁矿固溶体体系。由于存在有序-无序跃迁和Fe^<2+>/Fe^<3+>混合价态等可控因素，制备具有良好磁性的赤铁矿-褐铁矿固溶体薄膜存在诸多困难。研究了螺旋溅射制备固溶体薄膜的最佳工艺条件，以精确控制残余氧压力和衬底温度。薄膜在室温下表现出磁阻等磁性半导体特性。第二个课题是利用反铁磁层的自旋翻转跃迁来控制铁磁层的磁性结构。只有外延赤铁矿薄膜表现出独特的自旋翻转转变。采用螺旋溅射法制备了赤铁矿/尖晶石铁氧体双层薄膜，并对其自旋翻转转变前后的磁性能进行了研究。由于尖晶石铁氧体层具有较大的面内磁各向异性，导致赤铁矿层的自旋翻转转变消失。我们首先发现了氧化物磁层之间的90°交换耦合。遗憾的是，我们无法实现所提出的自旋控制技术，但我们可以在明确定义的氧化铁薄膜的制备技术及其结构，磁性和电子性能方面获得巨大的成果。