Using in-situ magneto-optical Kerr effect (MOKE) measurements and phenomenological modeling, we study the tunability in both the magnetization anisotropy and magnetic coupling of Fe nanodots on a curved Cu(111) substrate with varying vicinity. We observe that, as the terrace width w decreases, the magnetization anisotropy increases monotonously, faster when w is smaller than the nanodot diameter d. In contrast, the magnetic coupling strength first also increases till w ~ d, after which decreases steeply. These striking observations can be rationalized by invoking the counterintuitive dimensionality variation of the surface electrons mediating the inter-dot coupling: the electrons are confined to be one-dimensional (1D) when w ≥ d, but become quasi-2D when w < d due to enhanced electron spillover across the steps bridged by the nanodots.
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