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

主要结果：1。我们在最简单的氧化铜（CuO）中掺杂了空穴。我们发现CuO中反铁磁性的抑制是非常迅速的。此外，还观察到类似电荷条纹的秩序。我们还从μSR研究中获得了磁相分离的证据，证明了与电荷条纹相关的自旋顺序。因此，我们澄清了电荷条纹，这被认为是高温超导体的关键性质，在最简单的CuO.2化合物中发展。制备了氧化铜纳米粒子，并对其磁性变化进行了研究。我们发现纳米CuO中的磁转变温度急剧降低，显示出戏剧性的有限尺寸效应。这是第一个直接证明反铁磁系统中磁转变温度急剧下降的报告。我们发现了天然Cu_2Cl(OH)_3铜酸盐的自旋玻璃性质。此外，我们还发现它是一个新的具有d电子自旋的几何受挫系统。我们发现自旋涨落与磁有序共存。这一发现为材料方面和磁性（d电子自旋）方面的几何挫折研究开辟了一条新的途径。作为一种材料路线，它提供了一个以M为过渡金属和X卤素的大量M_2X(OH)_3的新体系。这些发现部分反映在诸如《物理评论快报》等科学杂志上发表或接受发表的15篇论文中。

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.