A位有序钙钛矿CdMn3Mn4O12高压单晶制备及其物性研究

In magnetoelectric multiferroics, the long-range spin ordering and ferroelectric polarization coexist and even strongly couple with each other, leading to abundant physics and promising applications. Base on this, exploration and research of novel multiferroics and physical mechanism in it are important research directions of multiferroic. Owing to exotic orbital ordering and the couple of it with magnetic ordering, the A-site ordered perovskite CdMn3Mn4O12 shows very novel physical properties. However, there are few reports about its physical properties at present. In this project, the large size and high quality CdMn3Mn4O12 single crystal grown under high temperature and high pressure conditions for the first time, will be investigated on its magnetic and multiferroic in the lower temperature magnetic phase. On this basis, we will explore new physical mechanism of multiferroic where ferroelectric polarization is induced by or related to orbital ordering. Moreover, we will study regulatory role that pressure have for multiferroic and search new physical phenomenons in it, with high pressure technology. These will provide a new solution of growing large size and high quality CdMn3Mn4O12 single crystal under high temperature and high pressure. What’s more, we will discover a new physical mechanism of multiferroic where ferroelectric polarization is induced by or related to orbital ordering closely. Probably, that is a new approach to large electric polarization and strong magnetoelectric coupling multiferroics.

在磁电多铁性材料中，磁有序和铁电极化的相互共存甚至强烈耦合具有丰富的物理内涵与应用前景。基于此，探索和研究新型多铁性材料及其物理机制是多铁性的重要研究方向。独特的轨道序以及轨道序与磁有序的强烈耦合使得A位有序钙钛矿CdMn3Mn4O12具有非常新颖的物理性质。目前，关于其物性研究的报道很少，本项目首次尝试利用高温高压手段生长大尺寸高质量的CdMn3Mn4O12单晶，借助多种研究手段探究33K处低温磁相变以及表征低温磁相新颖的物理性质，着重研究其多铁性及其多铁性物理机制。此外，还将利用高压技术研究压力对CdMn3Mn4O12单晶多铁性行为的调控作用和探索高压下其新奇的物理现象。通过本项目的研究，将发展一种在高温高压条件下生长大尺寸高质量单晶的方法，更重要的是，将揭示一种轨道序诱导的或者与其轨道紧密关联的全新多铁性物理机制，希望为合成大铁电极化和强磁电耦合的多铁性材料提供新的思路。

在磁电多铁性材料中，磁有序和铁电极化的相互共存甚至强烈耦合具有丰富的物理内涵与应用前景。基于此，探索和研究新型多铁性材料及其物理机制是多铁性的重要研究方向。独特的轨道序以及轨道序与磁有序的强烈耦合使得A位有序钙钛矿CdMn3Mn4O12具有非常新颖的物理性质。本课题利用高压高温以及助熔剂成功合成了CdMn3Mn4O12单晶。当温度降至TN1 = 88 K时CdMn3Mn4O12开始发生连续的顺磁-反铁磁相变，并在Tset = 63 K形成非共线的反铁磁结构。伴随着顺磁-反铁磁相变，CdMn3Mn4O12形成极化的磁点群1，自旋诱导的铁电极化随之发生。另外，在Tset以下，CdMn3Mn4O12具有大的铁电极化，且能够被外磁场有效地调控，表明CdMn3Mn4O12具有显著的磁电耦合效应。因此，同时具备大的铁电极化与强的磁电耦合效应，使CdMn3Mn4O12单晶不仅具有重要的研究意义，同时也具有潜在的应用价值。