Interlayer Exchange Coupling across Graphene and h-BN junctions*

Cobalt (Co)|Graphene and Co|hBN junctions are of great interest for graphene spintronics [1,2,3]. We present a comparative study of interlayer exchange coupling (IEC) between Co layers across graphene and hBN using first-principles calculations. IEC is calculated as a function of Co thickness for single graphene and hBN layer for three different FCC arrangements, namely AB, AC and BC. A RKKY type oscillatory exchange coupling constant alternating between strongly antiferromagnetic (AF) and weakly ferromagnetic (FM) is found. In FCC Co, the largest IEC is -200 meV for 5 monolayers of Co for AB type stacking whereas the HCP Co yields a coupling strength of -229 meV for AC type stacking, respectively. Finally, IEC as for hBN layer shows opposite phase for AB (12 meV) and AC/BC (-15 meV) FCC stackings. Thus, a control over the ICE gives a tunable parameter for synthetic antiferromagnetic structures in spintronics [4].
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[2] C. Vo-Van et al, New J. Phys. 12, 103040 (2010).
[3] H. X. Yang et al, Nano Lett. 16, 145 (2016).
[4] P. Gargiani et al, Nature Comm. 8, 699 (2017).