Spin Gap States in Exotic Low-Dimensional Molecular Magnets

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(1) We studied the organic radical, m-MPYNN, that formed an S=1 Kagome lattice in the crystals of m-MPYNN・X (X=I, ClOィイD24'ィエD2 BFィイD24ィエD2). The ground state was a spin gap state with Δ/kィイD2BィエD2=0.24 K. The extension of the methyl group in m-MPYNN resulted in collapses of the Kagome lattice and the spin gap state.(2) [Ni(dmit)ィイD22ィエD2] formed a spin-ladder structure in the crystal of p-EPYNN・[Ni(dmit) ]ィイD22ィエD2], which was a topic of in the study of low-dimensional magnetic materials, In this project we investigated a solid solution system p-EPYNN・[Ni(dmit) ]ィイD22ィエD2]ィイD21-xィエD2・[Au(dmit) ]ィイD22ィエD2]ィイD2xィエD2. The doping of non-magnetic [Au(dmit) ]ィイD22ィエD2]- brought about paramagnetic lattice defects in the spin ladder with a extended spin polarization.(3) We started the study of cyclic thioaminyl (NS) radicals and found a very interesting phase transition of TTTA. The phase transition occurred between a paramagnetic high-temperature phase and a diamagnetic low-temperature phase with a surprisingly large hysteresis loop. Since the room temperature was included in the loop, TTTA exhibited room-temperature magnetic bistability.