Magnetooptical Studies of Organic/Ferromagnetic Hybrid Structures

Organic semiconductors (OS) are desirable for spin-based devices because of their long spin coherence times due to low spin-orbit coupling. The use of ferromagnets (FM) to inject and detect spin polarization in OS has recently been demonstrated through experiments on organic spin valves (i.e. FM/OS/FM trilayer devices). An important issue for these devices is the spin-dependent properties of the FM/OS interface. To investigate this issue, layered FM/OS hybrid structures are fabricated using molecular beam epitaxy (MBE). Ultrathin single-crystalline Co films on Cu(100) substrate serve as the model FM layer, whose magnetic properties are characterized by in situ magneto-optic Kerr effect (MOKE). The structural properties of the Co film are characterized by RHEED and STM. Subsequently, wedged OS overlayers (e.g. Alq$_{3}$, Gaq$_{3})$ are deposited onto the FM film and in situ optical studies are performed. First, the effect of the OS on the magnetic properties of the Co layer is investigated using MOKE. Second, the effect of the FM layer on photo-excited carriers in the OS is investigated using polarization-resolved photoluminescence.