A suitably chosen thin layer inserted between a ferromagnetic electrode and an organic semiconductor allows control over the polarization of the injected spins. Among the advantages that organic semiconductors possess over conventional inorganic semiconductors is the relative ease with which their electronic structure can be modified through well-developed methods of synthesis. The weakness of coupling mechanisms can be a strength when envisaging possible spintronic devices, but it also precludes certain experiments that could probe the spin polarization of the mobile charge carriers. To overcome the difficulty of directly determining the spin polarization of injected charge carriers in organic semiconductors, the team led by Alan Drew pioneered a complex but elegant technique of measuring the local internal magnetic field by implanting (positive) muons and measuring the direction and timing of the positrons emitted in their decay.
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