Tuning the ferromagnetic coupling of Fe nanodots on Cu(111) via dimensionality variation of the mediating electrons.

ABSTRACT

Using in situ magneto-optical Kerr effect 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 monotonically, faster when w is smaller than the nanodot size d. In contrast, the magnetic coupling strength also increases until w approximately d, after which it decreases steeply. These striking observations can be rationalized by invoking the counterintuitive dimensionality variation of the surface electrons mediating the interdot coupling the electrons are confined to be one dimensional (1D) when w > or = d, but become quasi-2D when w < d due to enhanced electron spillover across the steps bridged by the nanodots.