DISCOVERY OF A QUASI-1D ORGANIC FERROMAGNET, P-NPNN

We discovered that an organic radical crystal, p-nitrophenyl nitronyl nitroxide (p-NPNN), is a quasi-1D ferromagnet induced by unpaired electrons on radicals. The magnetization and the susceptibility of the triclinic gamma-phase crystal are very well represented by the Bethe-ansatz solution of the S = 1/2 1D Heisenberg ferromagnet with nearest-neighbor coupling J congruent-to 4.3 K. Low-temperature specific heat and ac susceptibility measurements revealed that the crystal undergoes a ferromagnetic transition at 0.65 K, The interchain coupling J' was estimated to be about 0.1 K.