Experimental χ^-1(□) versus polar angle θ for sample 2 (40 ML Fe/Si(001)): θ=0° corresponds to the [100] direction, one notes four maxima at θ≈30º, 60°, 120° and 150°), the arrows indicate the minor maxima at θ≈90° and 180°(0°). Simulations using the determined anisotropy constants K_n taking into account the amplitude A_m^" (histogram in insert) and phase θ_m of the Fourier spectrum for m ≤ 8 (◙) and m ≤ 12 (•), respectively.

The experimental ΔH versus azimuthal angle θ (□) for sample 2. The simulations using the determinate anisotropy constants K_n by taking into account the amplitude A_m^" (histogram in inset) and phase θ_m of the Fourier spectrum for m ≤ 8 (◙) and m ≤ 12 (•), respectively.

TBIIST data for a 50 ML iron film on Si(1 1 1): Open symbols (◯, □) correspond to an incremental polar angle Δθ=2.5 (144 points) and full symbols (•, ■) represent measurements done with Δθ=10. The maxima of the χ-1 correspond to the easy axis of the 6th order in-spin contribution and coincide with the equivalent [121] directions.