6533b860fe1ef96bd12c2e3f

RESEARCH PRODUCT

Spin-polarized scanning tunneling microscopy and spectroscopy of ultrathinFe∕Mo(110)films usingW∕Au∕Cotips

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We report on magnetic contrast observed in low-temperature spin-polarized scanning tunneling microscopy (SP-STM) of Fe nanowires deposited on Mo(110) using tungsten tips covered by $\mathrm{Au}∕\mathrm{Co}$ thin films. Due to the spin reorientation transition of Co films on Au an out-of-plane magnetic sensitivity is obtained for tips with thin cobalt films (up to 8 monolayers of Co), while for thicker Co coverages an in-plane magnetization component can be probed. Using $\mathrm{W}∕\mathrm{Au}∕\mathrm{Co}$ tips with out-of-plane magnetic sensitivity we show that the one (ML) and two (DL) atomic layers thick Fe nanowires prepared using step flow growth on a Mo(110) crystal are perpendicularly magnetized. The reorientation of the tip sensitivity axis has been confirmed by SP-STM measurements of thicker $\mathrm{Fe}∕\mathrm{Mo}(110)$ films, where an in-plane easy axis has been observed for islands thicker than 3 ML. Spin-resolved spectra were measured using the $\mathrm{W}∕\mathrm{Au}∕\mathrm{Co}$ tips for ML, DL and thicker $\mathrm{Fe}∕\mathrm{Mo}$ films. The spectra reveal strong characteristic peaks at $0.4\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for ML Fe, and at $\ensuremath{-}0.08\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and $0.78\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for DL Fe. Peak positions and intensities depend on the relative orientation of tip and sample magnetization. Spin-resolved spectroscopic data obtained for different tips are compared.