  The utilization of large-area graphene grown by chemical vapour deposition
(CVD) is crucial for the development of scalable spin interconnects in
all-spin-based memory and logic circuits. However, the fundamental influence of
the presence of multilayer graphene patches and their boundaries on spin
dynamics has not been addressed yet, which is necessary for basic understanding
and application of robust spin interconnects. Here, we report universal spin
transport and dynamic properties in specially devised single layer, bi-layer,
and tri-layer graphene channels and their layer boundaries and folds that are
usually present in CVD graphene samples. We observe uniform spin lifetime with
isotropic spin relaxation for spins with different orientations in graphene
layers and their boundaries at room temperature. In all the inhomogeneous
graphene channels, the spin lifetime anisotropy ratios for spins polarized
out-of-plane and in-plane are measured to be close to unity. Our analysis shows
the importance of both Elliott-Yafet and Dyakonov-Perel mechanisms, with an
increasing role of the latter mechanism in multilayer channels. These results
of universal and isotropic spin transport on large-area inhomogeneous CVD
graphene with multilayer patches and their boundaries and folds at room
temperature prove its outstanding spin interconnect functionality, beneficial
for the development of scalable spintronic circuits.
