topological insulator with the Z 2 indices of (0; 111), which exhibits topological surface states on the (001) surface.

Fe3GeTe2 have proven to be of greatly intrigue. However, the underlying mechanism behind the varying Curie temperature (Tc) values remains a puzzle. This study explores the atomic structure of Fe3GeTe2 crystals exhibiting Tc values of 160, 210, and 230 K. The elemental mapping reveals a Fe‐intercalation on the interstitial sites within the van der Waals gap of the high‐Tc (210 and 230 K) samples, which are observed to have an exchange bias effect by electrical transport measurements, while Fe intercalation or the bias effect is absent in the low‐Tc (160 K) samples. First‐principles calculations further suggest that the Fe‐intercalation layer may be responsible for the local antiferromagnetic coupling that gives rise to the exchange bias effect, and that the interlayer exchange paths greatly contribute to the enhancement of Tc. This discovery of the Fe‐intercalation layer elucidates the mechanism behind the hidden antiferromagnetic ordering that underlies the enhancement of Tc in Fe3GeTe2.

The equilibrium geometric structures, relative stabilities, electronic stabilities, and electronic and magnetic properties of the Au n C and Au n+1 (n=1-9) clusters are systematically investigated using density functional theory (DFT) with hyper-generalized gradient approximation (GGA). The optimized geometries show that one Au atom added to the Au n-1 C cluster is the dominant growth pattern for the Au n C clusters. In contrast to the pure gold clusters, the Au n C clusters are most stable in a quasi-planar or three-dimensional (3D) structure because the C dopant induces the local non-planarity, with exceptions of the Au 6,8 C clusters who have 2D structures. The analysis of the relative and electronic stabilities reveals that the Au 4 C and Au 6 clusters are the most stable in the series of studied clusters, respectively. In addition, a natural bond orbital (NBO)

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