The exclusion of excited triplets as dominating paramagnetic species in doped PPy

Abstract

The deviations from the Curie susceptibility were observed for doped polypyrrole (PPy). Here, we examined the possibility that exited triplet species resulting from the combination between polarons yield such deviations. For the examination, the electron spin transient nutation (ESTN) method was applied to directly determine the spin quantum number of observed spins in the ESR spectra. The nutation experiments revealed the absence of a peak corresponding to S=1 and, moreover, the FID spectra denied the definite coexistence of two species. Thus, we conclude that the excited triplets should be excluded as main species giving the non-Curie susceptibility. In contrast, the doping-level dependences of the susceptibility were well explained in terms of the superposition of the Curie susceptibility and the Pauli one. Therefore, we conclude that the non-Curie components observed for doped PPy are attributed to the Pauli susceptibility as reported for several conducting polymers.