Polymorphism and Magnetism of Organic Radical Crystals

有机自由基晶体的多晶型和磁性

基本信息

批准号：
07640767
负责人：
KINOSHITA Minoru
金额：
$ 1.28万
依托单位：
Science University of Tokyo in Yamaguchi
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640767/
关键词：
Organic ferromagnet Ferromagnetic interactoin Phase transition Polymorphism Galvinoxyl p-NPNN Hydrogen bond Crystal structure

项目摘要

Organic radicals of galvinoxyl and p-nitrophenyl nitronyl nitroxide (p-NPNN) playd crucial roles in the discovery of purly organic ferromagnet. These two and some related compounds exhibit polymorphism and variety of magnetism. This was quite important in elucidating the mechanism of magnetic interactions, because the polymorphic forms are closely related to one another in crystal structure. Galvinoxyl exhibits ferromagnetic interaction in the high temperature phase, but it is non-magnetic below 85K.The crystal structure is known for the high temperature phase, but it is unknown at low temperature. In this project, we have tried to determine the crystal structure of its low temperature phase. We could obtain the x-ray diffraction pattern at about 10K.However, the crystal became twinned and extra spots appeared prevented us from final analysis of the pattern. We then tried to find a way to cool the crystals without crushing at the phase transtion temperature. Various ways could not succeed. During the course of testing various ways, however, we could succeed in finding the way to surpress the phase transition by applying pressure and to maintain the ferromagnetic interaction down to low temperature. As for the phase transitions in p-NPNN,model calculation indicates an importance of librational motion of the molecules in exhibiting the polymorphism.

甘谷氧基和硝基苯基硝基硝基氧化物（P-NPNN）的有机自由基在发现纯粹有机的铁磁铁中至关重要的作用。这两种和一些相关的化合物表现出多态性和多种磁性。这在阐明磁相互作用的机理方面非常重要，因为多态形式在晶体结构上彼此密切相关。葡萄干氧基在高温相中表现出铁磁相互作用，但在85K以下的非磁性。晶体结构以高温相闻名，但在低温下是未知的。在这个项目中，我们试图确定其低温阶段的晶体结构。我们可以在约10k处获得X射线衍射模式。但是，晶体变得扭曲了，似乎额外的斑点使我们无法对模式进行最终分析。然后，我们试图找到一种冷却晶体的方法，而无需在相位温度下压碎。各种方式无法成功。但是，在测试各种方式的过程中，我们可以成功地通过施加压力并将铁电磁相互作用降至低温来找到相反的方法。至于P-NPNN中的相变，模型计算表明该分子在表现多态性中的文库运动的重要性。