Magnetometric analysis of the interaction of Ni(111) with oxygen

Abstract

The interaction of oxygen with Ni(111) films on Re(0001), consisting of 18–50 atomic layers, was analyzed using LEED, AES and torsion oscillation magnetometry in situ in UHV (U-TOM) at room temperature. The sequence of rapid chemisorption up to θ = 13, followed by slow oxidation to 3 layers NiO, by lateral growth of islands, known from bulk crystals, has been confirmed. The initial sticking coefficient is determined to be So = 0.52 ± 0.1; it persists up to θ = 0.2. In the chemisorption state θ = 13 a minimum Smin ≤ 0.005 is observed. For the initial chemisorption (θ ≤ 0.2) the reduction of magnetic moment per O atom, ΔμOx, in comparison with the metallic Ni moment μNi, is given by ΔμOx = -4.5μNi. It is reduced to ΔμOx = -3.8μNi for θ = 13. The total reduction Δm of the magnetic moment saturates at ∼ 100 L with Δm = -2.7mML (moment mML of bulk monolayer Ni), corresponding to 3 monolayers of antiferromagnetic NiO. The surface anisotropy field is reduced from 9.9 ± 1 T for the free surface to 0 ± 1 T, both for the chemisorbed and the oxidized surface.