Crystalline Engineering using High Magnetic Field for Fabrication of Functional Materials

本项目的目的是研究磁场对熔体生长过程的影响，并澄清几种新型材料的磁性。为此，我们选择了高温超导体如RE123系和铋系，热电材料如铋钴酸盐和Ca12Al14O33用于光电应用。阐明了ErBa2Cu3Oy、Ca12Al14O33和(Bi.Pb2Sr2Co2Oy)熔体生长过程中的磁场效应。浮区法对结晶度的影响不明显，但对氧泡行为和阳离子在液-固界面上的分配系数有一定的正向影响。在包晶反应的情况下，观察到结晶度的提高，并对磁场控制层状氧化物的取向进行了深入的研究。我们研究了不同层状体系中局部结构变化和磁性离子引起的磁各向异性和易磁化轴的变化。在RE123体系中，发现稀土离子不仅对易磁化轴起着决定性的作用，而且对磁场取向的决定因素也起着决定性的作用。在最好的情况下，控制的最小磁场估计在1T左右，这个值比通常的超导磁体小一个数量级。

The purpose of this project is investigation on effects of magnetic field to the melt-growth process and clarification of magnetic properties of several novel materials. For this purpose we have chosen high temperature superconductors such as RE123 system and Bi system, thermoelectric materials such as bismuth cobaltite and Ca12Al14O33 for optoelectronic applications. Effects of magnetic fields during melt growth for ErBa2Cu3Oy, Ca12Al14O33 and (Bi.Pb)2Sr2Co2Oy were clarified. While there were not clear effect on crystallinity but several positive effects were observed on the behavior of oxygen bubbles and distribution coefficient of cations at liquid-solid interface in a floating zone method. In the case of peritectic reaction, improvement of crystallinity was observed and the control of orientation in layered oxide by magnetic field has been also intensively studied. We have investigated changes of magnetic anisotropy and easy axis of magnetization induced by locally structural changes and magnetic ions in various layered systems. In the case of RE123 system, it was found that RE ions had crucial role not only to easy axis of magnetization but also determination factor of magnetic field for orientation. In best case minimum magnetic field for control of was estimated around 1T, and this value was one order of magnitude smaller than that of usual superconducting magnet.