Measurement of spin transport properties and spin coherence in molecular semiconductors

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The purpose of this project is to estimate spin coherence in molecular semiconductors precisely. In the first stage of the project, I was provided a molecular spin valve device from a collaborator in Italy (Dr. V. Dediu) and tried to measure spin precession of propagating spins in molecular semiconductors, which is called as Hanle effect. However, no such effect was observed due to less reliability of spin injection into molecules in the device. He nce, in the second stage, experimental investigations of an interfacial electronics structures between molecular semiconductor single crystal and ferromagnetic metals and modulation of the electronic structure were implemented, in addition to a search for a new oxide ferromagnet as a good spin source for molecular semiconductors. Both were successfully carried out. In the final stage, a new spin injection method, dynamical spin pumping, was introduced, and spin injection into a zero-gap molecular semiconductor, single-layer graphene, was successfully demonstrated and spin coherence was precisely measured. This project revealed serious problems in earlier studies of molecular spintronics, and enabled an establishment of a novel spin injection method into molecular semiconductors.