X-ray absorption and magnetic circular dichroism signals from hexagonal boron nitride/Ni(111) interface

Otomo, Manabu; Matsumoto, Yoshihiro; Yamamura, Noyuri*; Entani, Shiro; Avramov, P.; Naramoto, Hiroshi*; Amemiya, Kenta*; Fujikawa, Takashi*; Sakai, Seiji

Graphene has been intensively studied in the last few years for its long spin coherent length. The performance of graphene spintronic devices, however, are strongly influenced by poor spin injection efficiency at graphene/ferromagnetic metal (FM) interface. A promising solution for improving spin injection efficiency is to insert a tunnel barrier between graphene and FM. In this study, we propose hexagonal boron nitride (h-BN) as a novel tunnel barrier for graphene spintronics. It was revealed that the N K-edge and B K-edge absorptions exhibit XMCD signals in response to the Ni magnetization. It was also found that the smaller incidence angle between the Ni magnetization and the X-ray propagation direction leads to larger XMCD signals. The nature of the spin polarization was discussed in connection with the energy and angle dependences of the XMCD signals, and contribution from magnetized Nickel atoms was proposed.