Nanostructure physics in copper oxides-the relation with unconventional properties of high-temperature superconductors and application of new properties

主要结果：1.在CuO最简单的氧化铜中掺杂空穴。我们发现CuO中反铁磁性的抑制是非常迅速的。此外，还观察到了带电条状有序结构。我们还从μ的SR研究中获得了磁相分离的证据，这表明了电荷条纹相关的自旋有序。因此，我们澄清了被认为是高温超导体的关键性质的电荷条纹是在最简单的CuO2化合物中形成的。我们制备了CuO纳米粒子，并研究了其磁性的变化。我们发现纳米CuO的磁相变温度显著降低，表现出明显的有限尺寸效应。这是第一次有直接证据表明反铁磁系统的磁相变温度显著降低。3.我们在天然Cu2Cl(OH)3中发现了自旋玻璃的性质。此外，我们还发现它是一个新的具有d电子自旋的几何受阻系统。我们发现自旋涨落和磁序是共存的。这一发现为研究几何受挫开辟了一条新的途径，无论是在材料方面，还是在(d电子自旋的)磁性方面。作为一种物质路线，它提供了一种新的M_2X(OH)_3体系，其中M是过渡金属和X卤素。这些发现部分反映在15篇发表或接受发表在科学杂志上的论文中，如《物理评论快报》。

Main results :1.We doped holes into the simplest copper oxide of CuO. We have found that the suppression of antiferromagnetism in CuO is dramatically rapid. Moreover, charge-stripe-like order has been observed. We have also obtained evidences of the separation of magnetic phase which suggests charge-stripe-associated spin order from μSR study. We therefore clarified that the charge-stripe, which is considered a key property for the high-temperature superconductors, develops in the simplest compound of CuO.2.We prepared nanoparticles of CuO and investigated the change in magnetism. We have found that the magnetic transition temperature in nanoparticle CuO is drastically reduced, demonstrating a dramatic finite-size effect. This is the first report of direct evidence of a drastic decrease of the magnetic transition temperature in antiferromagnetic system.3.We have found spin-glass properties in natural cuprates of Cu_2Cl(OH)_3. Furthermore, we have found that it is a new geometrically frustrated system with d-electron spins. We found the co-existence of spin fluctuation and magnetic order. This discovery uncovers a new route for the study of geometric frustration both in the material aspect as well as in the magnetism (of d-electron spins). As a material route, it provides a new system of M_2X(OH)_3 with a huge number where M is transition metal and X halogen.These discoveries are partly reflected in 15 papers published or accepted for publication in scientific magazines such as Physical Review Letters.