▎ 摘　　要

Here the magnetotransport properties of vertical spin valve structures incorporating graphene (Gr), Gr/Au and Gr/Al2O3 intervening layers are elucidated. An in-Plane magnetic field is obliquely applied to the device with the purpose to vary the relative magnetizations of ferromagnetic electrodes (Co and Ni). The relative magnetoresistance (MR) of Co/Gr/Ni is enhanced from similar to 0.16% to 0.57% by simply passivating the bottom Ni electrode with thin Au film. On the other hand, depositing Al2O3 on the bottom ferromagnetic layer in such a spin valve junction not only increases the magnitude of MR (similar to-0.52%) but also reverses its polarity. Furthermore, the linear current-voltage characteristics for graphene and graphene/Au spin valve devices specifies ohmic contact, while non-linear curves indicate tunneling behavior for graphene/Al2O3 device. (C) 2017 Elsevier B.V. All rights reserved.