Giant negative magnetoresistance of one-dimensional conductor TPP[Fe(Pc)(CN)2]2

We found the giant negative magnetoresistance in TPP[Fe(Pc)(CN) 2 ] 2 below 50K. The magnetic susceptibility shows a highly anisotropic Curie behavior. Under the field along the α-axis (the c-axis), we observed the large (small) negative magnetoresistance and the large (small) magnetic susceptibility. This experimental results suggest the π-d interaction between the one-dimensional conduction electrons and the local magnetic moments. We proposed the field-induced reduction of the spin scattering of the conduction electrons by the local moments as the origin of the negative magnetoresistance. In the isostructural compound TPP[Co(Pc)(CN) 2 ] 2 without magnetic moments, we observed large positive magnetoresistance. The experimental result of the Co-compound suggests that the local moments are essential for the mechanism of the negative magnetoresistance of the Fe-compound.