Super-spin glass with hierarchical structure aimed for a brain-type memory

阐明了具有分级结构的超自旋玻璃和无定形氧化物磁体作为无规磁系统原型的磁性基本原理。对于前者，磁赤铁矿纳米晶沉淀在介孔中的介孔二氧化硅微粒的组装状态已被制造。法拉第效应测量表明，该材料在室温下具有超顺磁性。对于非晶氧化物磁体，含铁和稀土元素的氧化物玻璃表现出自旋玻璃或超自旋玻璃转变，而非晶EuZrO_3薄膜表现出折返自旋玻璃转变并伴有铁磁转变。这些磁相变的机制已被阐明。

Fundamentals of magnetism have been clarified for super-spin glass with hierarchical structure and amorphous oxide magnets which are prototype of random magnetic systems. For the former, an assemblage state of mesoporous silica microparticles with maghemite nanocrystals precipitated in the mesopores has been fabricated. The Faraday effect measurements reveal that the material show superparamagnetism at room temperature. As for the amorphous oxide magnets, oxide glasses containing both iron and rare-earth elements exhibit spin glass or super-spin glass transition, while amorphous EuZrO_3thin film shows re-entrant spin glass transition accompanied by ferromagnetic transition. The mechanism of these magnetic phase transitions have been elucidated.