Spin-orbit coupling in scattering of very low-energy spin-polarized electrons from Co film by (e,2e) spectroscopy

Energy and momentum distributions of correlated electron pairs excited by very low energy (9-30 eV) spinpolarized electrons from a thin Co film on a single crystal of W(110) were detected and analysed. Polarization of the incident electrons was perpendicular to the scattering plane. Spin effects are presented in form of asymmetry A = (I+ - I-)/(I+ + I-), where I+ and I- are two-electron spectra recorded with incident electrons polarization parallel or anti-parallel to the magnetization of the sample, respectively. Performing measurements at two opposite magnetizations of the sample and assuming negligible interference between spin orbit coupling and exchange effect in scattering, two component of asymmetry can be extracted, namely a spin-orbit asymmetry A(SO) and an exchange asymmetry A(ex). The spin-orbit component of the scattering asymmetry was analysed as a function of the primary energy. Contrary to normal expectations the value of spin-orbit asymmetry decreases with increase of the primary energy in the energy range from 9 to 30 eV.