Spin-Polarized Tunneling Spectroscopy of Co(0001) Surface States

Abstract

Spin-polarized tunneling was studied on Co surfaces of exchange coupled Co/Cu/Co samples, using an Fe tip. A spin-polarized surface state of Co(0001) was found to exist at $-0.43\mathrm{}\mathrm{eV}$ relative to $E_{\mathrm{F}}$, with FWHM of 0.23 eV in the spectra. The state exhibits negative magnetoresistance with an effective spin polarization of less than $-23\mathrm{}\%$, suggesting negatively high spin polarization of the surface state. Our first-principles calculations have supported the existence of the surface state. From the calculation, the state is identified as a minority spin $\overline{\Gamma }$-centered $d_z^2$-like surface state.