Electron capture spectroscopy ECS at Cr(100) and Ni(110) surfaces

The magnetic structure of surfaces of Cr and Ni which are commercial catalysts has been investigated by measuring the electron spin polarization (ESP) using electron capture spectroscopy (ECS) (capture of spin polarized electrons during grazing angle surface reflection of swift deuterons: D+ + e- = D0). At (100) surfaces of antiferromagnetic Cr at T = 293 K which is below the Neel temperature Tsub(N) = 310 K and ESP up to -(18 +- 2)% is found which clearly shows that the topmost surface layer of Cr(100) is ferromagnetic. In experiments at Ni(110) surfaces the temperature dependence of the magnetic surface structure is investigated by testing two-electron capture processes (D+ + 2e- = D-) as a simple new possibility to detect surface magnetic order. From the experiments there is evidence that the 'local' ferromagnetic order at Ni(110) surfaces exists up to 1.95 Tsub(C) (Curie temperature Tsub(C) = 631 K). (orig.)