Spin-dependent transport behavior in C₆₀ and Alq₃ based spin valves with a magnetite electrode (invited)

The spin-dependent transport behavior in organic semiconductors (OSs) is generally observed at low temperatures, which likely results from poor spin injection efficiency at room temperature from the ferromagnetic metal electrodes to the OS layer. Possible reasons for this are the low Curie temperature and/or the small spin polarization efficiency for the ferromagnetic electrodes used in these devices. Magnetite has potential as an advanced candidate for use as the electrode in spintronic devices, because it can achieve 100% spin polarization efficiency in theory, and has a high Curie temperature (850K). Here, we fabricated two types of organic spin valves using magnetite as a high efficiency electrode. C₆₀ and 8-hydroxyquinoline aluminum (Alq₃) were employed as the OS layers. Magnetoresistance ratios of around 8% and over 6% were obtained in C₆₀ and Alq₃-based spin valves at room temperature, respectively, which are two of the highest magnetoresistance ratios in organic spin valves reported thus far. The magnetoresistance effect was systemically investigated by varying the thickness of the Alq₃ layer. Moreover, the temperature dependence of the magnetoresistance ratios for C₆₀ and Alq₃-based spin valves were evaluated to gain insight into the spin-dependent transport behavior. This study provides a useful method in designing organic spin devices operated at room temperature.