Electron-Spin Polarization at Single-Crystalline Cr and Ni Surfaces Determined with Electron-Capture Spectroscopy

The spin polarization $P$ of electrons at Cr and Ni surfaces is measured with electron-capture spectroscopy. With use of one-electron capture at magnetized Cr(100)-$c(2\mathrm{}\times 2)$ surfaces at 293 K ($T_N=310\mathrm{}$ K), $P$ values up to -18% are found revealing ferromagnetic order at this surface. Utilizing two-electron capture at demagnetized Ni surfaces we find at 293 K ($T_C=631\mathrm{}$ K) $\mathrm{}\left|P\right|=94\%$ for Ni(110), $\mathrm{}\left|P\right|=72\%$ for Ni(100), $\mathrm{}\left|P\right|=47\%$ for Ni(111), and $\mathrm{}\left|P\right|=14\%$ for Ni(120). There is evidence that "local" ferromagnetic order at Ni surfaces exists even at $2T_C$.