MAGNETIC-MOMENTS IN CR THIN-FILMS ON FE(100)

The magnetism at the surface of a Cr film grown epitaxially on a Fe(10 0) whisker is observed as a function of Cr thickness by scanning elect ron microscopy with polarization analysis. Use of a wedge-shaped film of linearly increasing thickness allows the magnetism to be followed c ontinuously for 75 Cr layers. Over the temperature range measured from just below the Neel temperature of bulk Cr, T(N), to 1.8 T(N), the su rface magnetic moment is seen to persist and change direction with eac h additional Cr layer, but there are phase slips in this antiferromagn etic ordering, These are consistent with an incommensurate spin densit y wave (SDW) in the Cr film having a wavelength of 40 layers at T(N). An irregularity in the antiferromagnetic stacking order in the first f our layers is discussed and the behavior of the moments at the subsequ ent phase slip is examined. The limitations which prevent the determin ation of the surface magnetic moment from the spin polarization of sec ondary electrons are discussed.