1996 Fiscal Year Final Research Report Summary
Polymorphism and Magnetism of Organic Radical Crystals
| Project/Area Number |
07640767
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
機能・物性・材料
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| Research Institution | Science University of Tokyo in Yamaguchi |
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Principal Investigator |
KINOSHITA Minoru Science University of Tokyo Faculty of Science and Engineering Professor, 基礎工学部, 教授 (40011530)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Organic ferromagnet / Ferromagnetic interactoin / Phase transition / Polymorphism / Galvinoxyl / p-NPNN / Hydrogen bond / Crystal structure |
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| Research Abstract |
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.
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