Fig. 25: Asymmetry ratio R versus perpendicular momentum transfer L for the rods (1,0) and (0,1) of the (111) surface of the Co3Pt alloy.

The (1,0) rod has bulk Bragg peaks at L = 1 and 4. The non-zero values of R at these values of L are an indication of the bulk magnetisation of the sample. For 1 < L < 4 the non vanishing Rs are due to the magnetism of the Pt atoms at the surface. Similar considerations apply to the (0,1) rod.

The continuous curves are calculated by supposing that the Pt atoms at the surface may have a different magnetic moment than those of the bulk. The only free parameter in the model is the magnetisation of the surface Pt atoms, which was found to be about 1/2 that of the bulk atoms.