Pressure-Induced Ferromagnetic to Nonmagnetic Transition and the Enhancement of Ferromagnetic Interaction in the Thiazyl-Based Organic Ferromagnet γ-BBDTA・GaCl_4(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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A thiazyl-based ferromagnet, the γ-phase of BBDTA (i.e., benzo[1,2-d:4,5-d']bis[1,3,2]dithiazole)・GaCl_4, has a high ferromagnetic ordering temperature of 7.0K in organic radical ferromagnets. In this system, pressurization generated more compact molecular packing, resulting in that the ferromagnetic state at P=16.2kbar is stabilized over a temperature range of more than twice of the initial range. However, the saturation magnetic moment was reduced with increasing pressure, decreasing to about 12% of the initial value even at the low pressure level of P=1.0kbar. This suggests that the ferromagnetic molecular packing of the monoclinic γ-phase is easily transformed into that of the diamagnetic phase. Powder X-ray diffraction experiments revealed that the diamagnetic non-monoclinic (α- or β-) phase became stable instead of the monoclinic γ-phase across the pressure of 2.5-5.8kbar. The increase in the temperature of onset of ferromagnetic state occurs in the surviving ferromagnetic domain surrounded by the diamagnetic domains.
社団法人日本物理学会の論文
2008-12-15