Neutron Diffraction Study of p-electron Orgnic Magnets

1993 Fiscal Year Final Research Report Summary

• Project/Area Number: 04452052
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: 物性一般（含極低温･固体物性に対する理論）
• Research Institution: Ehime University
• Principal Investigator: TOMIYOSHI Shouichi Ehime Univ. Dep. Materi. Science and Engi. As. Prof., 工学部, 助教授 (50005922)
• Co-Investigator(Kenkyū-buntansha): AZUMA N. Ehime Univ. Faculty of General Education As. Prof., 教養部, 助教授 (00093914) ; YANO T. Ehime Univ. Dep. Materi. Science and Engi. Prof., 工学部, 教授 (50036240)
• Project Period (FY): 1992 – 1993
• Keywords: Organic Compound / Antiferromagnetism / Neutron Diffraction / Spin Strucure

Research Abstract

In the present study we investigated the magnetic properties of organic compound Triphenylverdazyl (TPV) by magnetization measurement and neutron diffraction using single crystal samples. We succeeded in growing fairly large single crystals of TPV using recrystalization method in acetone solution. Hexagonal plate crystals with maximum weight of 18mg which is enough for neutron diffraction experiments were obtained.
We measured magnetization using a vibrating sample magnetometer and a SQUID magnetometer. We found that magnetic susceptibility shows broad maximum around 5K indicating low dimensional mgnetic nature. Below T_N the magnetization abruptly increases due to onset of weak ferromagnetism which is the first observation in organic compounds. From the magnetic susceptibility below T_N the direction of the magnetic moment was estimated to be along the b-axis.
Neutron diffraction experiment was made using a triple-axis spectrometer TOPAN of Tohoku University at JRR-3 in Tokai. Magnetic neutron diffraction peak of (101) was observed, but other peaks were found to have very weak magnetic intensity. From these neutron diffraction data we determined magnetic structure of TPV.The magnetic moment on TPV molecule couples antiferromagnetically along the c-axis direction with the spins lying in the b-axis.
Our present work indicatesd that neutron diffraction is very useful for understanding the magnetism in organic compounds.

Research Products

• [Publications] S.Tomiyoshi 他: "Weak Ferromagnetism and Long Range Antiferromagnetic Ordering of Organic Radical Compound 2,4,6-Triphenylverdazyl" Phys.Rev.B.49(掲載予定). (1994)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] N.Azuma 他: "Molecular and Crystal Structures of Complexes of Stable Free Radical BDPA with Benzen and Acetone" Bull.Chem.Soc.Jpn.67. 31-38 (1994)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] N.Azuma 他: "Molecular and Crystal Structure of 9-[α(9H-Flouren-9-ylidene)-4-chlorobenzyl]-9H-Flouren-9-yl;an Organic Antiferromagnet with T_N=3.25K" J.Chem.Soc.Perkin Trans.2(掲載予定). (1994)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] S.Tomiyoshi, N.Azuma, M.Shoga, K.Yamada, Y.Yano and J.Yamauchi: "Weak Ferromagnetism and Long Range Antiferromagnetoc Ordering of Organic Radical Compound 2,4,6-Triphenylveerdazyl" Phys. Rev. B. Vol. 49 (in press). (1994)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] N.Azuma, T.Ozawa, and J.Yamauchi: "Molecular and Crystal Structures of Complexes of Stable Free Radical BDPA with Benzen and Acetone" Bull. Chem. Soc. Jpn.Vol. 67. 31-38 (1994)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] N.Azuma, T.Ozawa and J.Yamauchi: "Molecular and Crystal Structure of 9-[alpha(9H-flouren-9-ylidence)-4-chlorobenzyl]-9H-Floruen-9-yl ; an Organic Antiferromagnet with T_N=3.25K" J.Chem. Soc. Perkin Trans.Vol. 2 (in press). (1994)
  • Description: 「研究成果報告書概要(欧文)」より