Magnetic exchange force microscopy and spectroscopy on Fe/W(001)

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This work employs scanning probe techniques, particularly frequency-modulated atomic force microscopy (FM-AFM) and related methods like Kelvin probe force microscopy (KPFM), to investigate the structural, electronic, and magnetic properties of monolayer iron on tungsten (001) in ultra high vacuum and low temperatures. The study utilizes magnetic exchange force spectroscopy (MExFS) to experimentally access the exchange interaction between single iron atoms with antiparallel coupling for the first time. Iron grows pseudomorphically on W(001), resulting in highly strained layers. Variations in strain and hybridization with the substrate cause differences in electronic properties and magnetism, with distinct work functions observed in both layers, as mapped by KPFM. The second layer is ferromagnetic (FM) with in-plane anisotropy, while the first layer exhibits antiferromagnetic (AF) characteristics with out-of-plane anisotropy, confirmed by magnetic force microscopy (MFM). The AF alignment of magnetic moments in the monolayer is resolved using MExFM. MExFS measures the distance dependence of magnetic exchange interactions between a sharp magnetic tip and the antiferromagnetically ordered Fe monolayer, allowing for the extraction of interaction contributions. Experimental results are compared to ab initio calculations, revealing variations in MExFM contrasts based on the symmetry and stability of the probe tips. The study also char