The Origin of Organic Magnetoresistance Using Time-Domain Magnetic Spectroscopy

Abstract

Organic Magnetoresistance is defined as the change of resistance in an organic material, such as a conducting polymer, as a function of an imposed magnetic field. We demonstrate this effect in a Polypyrrole/ Polydimethylsiloxane complex by using a novel magnetic pulse system. The frequency spectrum of the current flowing through the sample reveals equally spaced reversed peaks in the current. We show that these peaks happen at the Lamour frequency for the dominant charge carrier of the system, namely polarons. This posits the origin Organic magnetoresistance as simple Rabi Oscillations rather than mechanisms based of bipolaron formation and singlet-triplet conversions. We directly estimate the effective polaronic mass in this complex. A semi classical theoretical approach is suggested to explain this effect as direct spin flipping in a time transient magnetic field. This is the first time that such an experimental approach has been applied in this field and the first time the effective polaronic mass has been measured in a conducting polymer.