Incident angle dependence of MCD at the Dy M₅-edge of perpendicular magnetic Dy_xCo_100-x films

X-ray absorption and magnetic circular dichroism spectra (XAS-MCD) of the Dy M_4,5-edges of Dy_xCo_100-x (x = 15-33) thin films are measured. The advantage of element and orbital selectivity in the XAS-MCD measurements enables us to directly observe the magnetic moments of specified elements. The MCD intensity at the Dy M₅-edge is maximum when the incident X-ray is normal to the surface and the incident angle dependence of the MCD intensity shows a sine curve. That gives us information about the angular distribution of the Dy magnetic moments with respect to the total magnetization direction and the opening angle of the cone. Applying the sum rule, the expectation value of orbital magnetic moment was estimated. The half opening angle of the random distribution of the moments were estimated and it was found that the angle has its minimum value around x = 20.