Organic Magnetoresistance

In recent years a broad range of magnetoresistance phenomena have been reported for organic-based semiconductors, conductors and magnets. Organic systems illustrating magnetoresistance, include molecular- and polymer-based nonmagnetic semiconductors[1], organic-based spin polarized magnetic semiconductors,[2] nonmagnetic conducting polymers, and ferromagnet/organic semiconductor/ferromagnet heterojunctions. Examples of each of these organic-based systems will be presented together with a discussion of the roles of magnetotransport mechanisms including interconversion of singlets and triplets, compression of the electronic wavefunction in presence of a magnetic field, quantum interference phenomena, effects of a ``Coulomb gap'' in $\pi $* subbands of organic magnetic semiconductors with resulting near complete spin polarization in conduction and valence bands of magnetic organic semiconductors.[2,3] Opportunities for magnetotransport in Ferromagnet/Organic Semiconductor/Ferromagnet heterojunctions will be discussed.[4] \\[4pt] [1] V.N. Prigodin \textit{et al.}, Synth. Met. \textbf{156}, 757 (2006); J.D. Bergeson \textit{et al.}, Phys. Rev. Lett. \textbf{100}, 067201 (2008) \\[0pt] [2] V.N. Prigodin \textit{et al}., Adv. Mater. \textbf{14}, 1230 (2002. \\[0pt] [3] J.B. Kortright \textit{et al}., Phys. Rev. Lett., \textbf{100}, 257204 (2008). \\[0pt] [4] J.D. Bergeson, \textit{et al.}, Appl. Phys. Lett. \textbf{93}, 172505 (2008).