EPR study of chemically synthesized polypyrroles soluble in organic solvents

Abstract

The results of electron paramagnetic resonance (EPR) experiments are reported for chemically synthesized polypyrroles soluble in organic solvents, which have different doping levels. Pauli susceptibility $({\ensuremath{\chi}}^{P})$ and the density of states $[{D(E}_{F})]$ are obtained from the temperature dependence of magnetic susceptibility. The ${\ensuremath{\chi}}^{P}$ and the ${D(E}_{F})$ increase as the doping level increases, which indicates that the system becomes more highly conducting. The electron spin-lattice relaxation time ${(T}_{1})$ is measured by using saturation methods. The ${T}_{1}$ decreases with increasing doping level at room temperature. This implies that the spin-lattice interaction easily occurs in the sample with the high concentration of dopants. The EPR linewidth $(\ensuremath{\Delta}H)$ linearly increases as temperature increases from 100 K to room temperature. We use a Korringa relaxation rate to account for the temperature dependence of the $\ensuremath{\Delta}H.$