Crystal growth and properties of novel multiferroic oxide compounds

像RMn2O5(R=稀土)这样的多铁性材料因其在磁性和铁电性质之间表现出强烈耦合而在磁电材料方面具有广阔的应用前景而受到极大的关注。本项目的目的是用两种不同的晶体生长方法：传统的熔剂法和流动溶剂浮区法(TSFZ)生长和研究复合RMn2-xFexO5和RMn2？xCoxO5氧化物(R=Y，Tb，Ho)的单晶。根据最近获得的多晶样品的数据，Fe和Co取代RMn2O5中的Mn的原因预计是温度的急剧上升(直到室温)，此时出现了强烈的磁电耦合和多铁性行为。尽管已有关于未掺杂RMn2O5晶体的研究结果，但没有关于取代单晶的数据报道。因此，首次生长的RMn2-xFexO5和RMn2-xCoxO5晶体将根据掺杂元素的性质、浓度水平、晶格中的价态和氧含量，研究它们的磁性和铁电性质，以及相应的有序温度和磁电效应。取代化合物的晶体生长有助于理解掺杂RMn2O5晶化过程中的基本问题，以及掺杂元素对磁电性能变化的影响，具有潜在的工艺应用价值。

There is an extremely increased interest to multiferroic materials such as RMn2O5 (R = rare earths) due to their promising applications as magnetoelectric materials those show strong coupling between magnetic and ferroelectric properties. The aim of this project is to grow and investigate single crystals of complex RMn2-xFexO5 and RMn2¿xCoxO5 oxides (R = Y, Tb, Ho) by two different crystal growth methods: by the conventional flux technique and the travelling solvent floating zone (TSFZ) technique. The reason of Fe and Co substitution of Mn in RMn2O5 is expected dramatic increase of temperatures (up to room temperatures), where strong magnetoelectric coupling and multiferroic behaviour appears, according to the recently obtained data on polycrystalline samples. In spite of the presence of the published results on investigation of undoped RMn2O5 crystals, no data were reported on the substituted single crystals. Therefore, the grown for the first time RMn2-xFexO5 and RMn2-xCoxO5 crystals will be studied with respect to their magnetic and ferroelectric properties, corresponding ordering temperatures and magnetoelectric effects depending on the nature of the doping element, its concentration level, valence states in the lattice and oxygen content. Crystal growth of the substituted compounds can help in understanding the fundamental problems in crystallization of doped RMn2O5 and the effects of doping element on variation of magnetoelectric properties for potential technological applications.