  We report observation of ferromagnetic (FM) ordering in organic
semiconductors, namely regio-regular poly (3-hexyl thiophene) (RRP3HT) and
1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM), in the
temperature range of 5-300 K in addition to magnetoresistance (OMAR) observed
in the diodes made from the same materials. Particle induced x-ray emission
spectroscopy confirms the presence of dilute magnetic impurities in the
materials mainly as residues from the synthesis process. However, upon blending
these two materials with FM signal, the FM ordering is suppressed by a huge
paramagnetic (PM) signal indicating ground state charge transfer formation in
the blend. Together with the magneto-transport studies, these results indicate
that OMAR response is observed in a device only when the corresponding active
materials are FM. In the diodes with P3HT:PCBM complex, that as a blend shows
PM response, OMAR vanishes almost completely. We propose that ferromagnetism in
the active material can have important correlation with the OMAR response in
the diodes.
