Magnetic properties in polypyrrole doped by series of dopants

Magnetic susceptibility and ESR linewidth are measured as a function of temperature in polypyrrole (PPy) doped with PF6−, AsF6−, ClO4−, BF4−, ToS−. Spin susceptibility by Schumacher-Slichter (ESR-NMR) technique shows both the temperature independent Pauli term ranging from 0.7 to 1.4×10−5 emu/mol-ring and the Curie term of 1 spin per 600~1500 rings, which is consistent with that obtained by SQUID measurement in the same sample. The temperature dependence of ESR linewidth is ascribed to the Elliott mechanism typical for the metallic electron spins, increasing monotonically with the temperature. This interpretation is also consistent with the ESR linewidth in polythiophene doped with ClO4− and AsF6−. Therefore, both the susceptibility and the ESR linewidth demonstrate the PPyʹs doped with several dopants to have a metallic electronic state.