Hysteretic electroluminescence in organic light-emitting diodes for spin injection

Organic light-emitting diodes with ferromagnetic contacts are fabricated, and their emission intensity is studied at room temperature for parallel and antiparallel magnetization configuration of anode and cathode. Sweeping the magnetic field applied parallel to the electrode allows the magnetization of the two electrodes to be switched independently. The electroluminescence intensity for the antiparallel magnetic configuration is found to be enhanced as compared to the parallel one. We show that this increase is not evidence of spin injection but is a consequence of the magnetic-field dependence of the electroluminescence intensity combined with magnetic stray fields from the electrodes.