Magnetotransport properties of graphene directly grown on permalloy in CPP configuration

Entani, Shiro; Naramoto, Hiroshi*; Sakai, Seiji

In the graphene spintronic devices, the control of the spin injection and ejection processes at the interfaces between graphene and ferromagnetic metal electrodes are crucial for the device operation. In this work, magnetotransport properties were studied for the vertical spin valve devices with two junctions of permalloy electrodes and a few-layer graphene interlayer. The graphene layer was directly grown on the bottom permalloy electrode by chemical vapor deposition. X-ray photoelectron spectroscopy showed that the permalloy surface fully covered with a few-layer graphene is kept free from oxidation and contamination even after dispensing and removing photoresist. This enabled fabrication of the current perpendicular to plane spin valve devices with a well-defined interface between graphene and permalloy. Spin-dependent electron transport measurements revealed a distinct spin valve effect in the devices. The magnetotransport ratio was 0.8% at room temperature and increased to 1.75% at 50 K. Linear current-voltage characteristics and resistance increase with temperature, indicating that ohmic contacts are realized at the relevant interfaces.