Exchange coupling and high-temperature transport in M(phthalocyanine)I conductors

From our analysis of the magnetic susceptibility in M(pc)I organic conductors, we are able to extract a carrier-mediated exchange interaction for Cu²⁺ spins in the alloy Cu_xNi_1-x(pc)I. We find that J_ed≈300 K. We also show that residual magnetic impurities must be present to account for the observed experimental trends. At high temperatures, we argue that the experimentally observed positive magnetoresistance is consistent with the standard semiclassical correction (ω_cτ)², indicating that in this regime, transport is diffusive and three dimensional.