Interaction Between Optically-Generated Charge-Transfer States and Magnetized Charge-Transfer States toward Magneto-Electric Coupling.

This article reports the magneto-dielectric studies on the coupling between optically generated CT states and magnetized CT states based on thin-film devices with the architecture of ITO/TPD:BBOT/TPD/Co/Al. The magnetized CT states are generated at the Co/TPD interface, generating a magneto-dielectric response with a broad, non-Lorentzian line-shape. The optically generated CT states are formed at the TPD:BBOT interfaces in the heterojunction under photoexcitation, leading to a magneto-dielectric signal with a narrow, Lorentzian line-shape. We find that combining the optically generated CT states and magnetized CT states yields a new magneto-dielectric signal with distinctive line-shape and amplitude in the ITO/TPD:BBOT/TPD/Co/Al device. The magneto-dielectric analysis indicates that there exists a coupling between optically generated CT states and magnetized CT states through the interactions between the magnetic Co/TPD interface and the optically excited TPD:BBOT heterojunction. Furthermore, we show that the coupling between optically generated CT states and magnetized CT states experiences Coulomb interactions and spin-orbital interaction by changing (i) the density of optically generated CT states and (ii) the separation distance between optically generated CT states and magnetized CT states. Clearly, this coupling provides a new approach to mutually tune magnetic and electronic properties through thin-film engineering by combining magnetic and organic materials.