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Bis(glycolato)copper(ii) [Cu(HOCH2CO2)2] shows a structural phase transition around 220 K under cooling and 270 K under heating, and ferromagnetic ordering at 1.1 K. Deuterium substitution of the hydroxyl groups in it induced a large shift in the structural transition temperature while no shift in the ferromagnetic transition temperature took place. [ABSTRACT FROM AUTHOR]

Three polymorphs, labeled α (plates), β (needles), and γ (blocks), of BBDTA(=benzo[1,2-d:4,5-d′]bis[1,3,2]dithiazole) · GaCl4 were obtained as a mixture of three polymorphs, by recrystallization at −23 °C. The γ-phase showed the ferromagnetic ordering at 7.0 K, in contrast to diamagnetic properties of the α- and β-phases. The crystal structure of the γ-phase exhibited a minimal overlap between the singly occupied molecular orbitals of neighboring molecules, in spite of short interatomic S⋯N distances. [Copyright &y& Elsevier]

Abstract: We examined the crystal structures and magnetic properties of heterocyclic thiazyl radicals and their molecular compounds. 1,3,5-Trithia-2,4,6-triazapentalenyl (TTTA) exhibited a room-temperature bistability between a paramagnetic high-temperature (HT) phase and a diamagnetic low-temperature (LT) phase. The phase control of TTTA was achieved by pressure and light irradiation. The conductivity of TTTA in the HT phase (10−8 Ω−1 cm−1) was increased by five orders of magnitude due to I2 doping. 1,3,2-Benzodithiazolyl (BDTA) also made a diamagnetic–paramagnetic phase transition above room temperature, but fresh samples always exhibited superheating and supercooling at the transition. The molecular compounds, TTTA·[Cu(hfac)2], BDTA·[Ni(mnt)2] and (Benzo[1,2-d:4,5-d′]bis[1,3,2]dithiazole (=BBDTA))·MCl4 (M=Ga and Fe) were found to include rather strong ferromagnetic interactions. [Copyright &y& Elsevier]

Abstract: A radical cation salt, BBDTA (= benzo[1,2-d:4,5-d′]bis[1,3,2]dithiazole)·GaCl4, has three polymorphs, labeled α, β and γ. The γ-phase shows a ferromagnetic ordering at 7.0K, and this Curie temperature (T C) is eminently high, in contrast to those of the other organic radical ferromagnets. We have investigated the pressure effects on the γ-phase of BBDTA·GaCl4 through ac magnetic susceptibility measurements under hydrostatic pressure up to 16.2kbar. The value of T C increases with linear fashion against pressure and exceeds 14K at 16.2kbar. By applying further pressure, it may exceed 16 K of the organic ferromagnet, TDAE-C 60 , which has the highest T C in organic materials. However, the real component of the ac susceptibility below T C is remarkably suppressed with increasing pressure and, at around 2kbar, it decreases down to 3.5% of that at ambient pressure. Those pressure effects might originate from the pressure-induced structural transformation from the ferromagnetic γ-phase to the diamagnetic α- and/or β-phases and the enhancement of the intermolecular interactions in the surviving γ-phase. [Copyright &y& Elsevier]

Abstract: We have observed the magnetic susceptibility and the magnetization of an organic S=1 Heisenberg magnet m-EPYNN·BF4·1/3(ethanol) which has a slightly distorted two-dimensional Kagomé lattice and antiferromagnetic interactions. In contrast to the nonmagnetic ground state of m-MPYNN·BF4 without the lattice distortion, the m-EPYNN salt shows a large zero-field susceptibility χ below 1K. The Weiss temperature derived by fitting 1/χ below about 1K to the Curie–Weiss law is positive, which indicates that the system is ferromagnetic at low temperatures. The ferromagnetic tendency of the ground state is also suggested by the magnetization curve at 90mK, where a steep increment reaching at about 1/3 of the saturation magnetization is observed below a few kOe. [Copyright &y& Elsevier]

Abstract: An organic magnet shows a ferromagnetic transition at that is a typical long-range ordering of the Heisenberg ferromagnetic chains with intra-chain interaction of , induced by only a ferromagnetic inter-chain interaction of . A sample with impurity shows a transition at 0.3K that is 0.12K lower than that of the pure sample. The impurity that was contained in the synthesis is considered to be the -phase that is an antiferromagnet of antiferromagnetic chains. The amount of the impurity is estimated to be about 20%. In terms of the mean field calculation, the reduction of corresponds to a smaller inter-chain interaction to be . [Copyright &y& Elsevier]