Orbital contribution to the 3d magnetic moment in ferromagnetic Cu3Au-type transition-metal-Pt alloys probed by soft-x-ray magnetic circular dichroism

Magnetic circular dichroism in the soft-x-ray absorption spectrum in the $2\stackrel{\ensuremath{\rightarrow}}{p}3d$ excitation region of the transition-metal element is measured for ferromagnetic ${\mathrm{Cu}}_{3}\mathrm{A}\mathrm{u}\ensuremath{-}\mathrm{t}\mathrm{y}\mathrm{p}\mathrm{e}$ alloys, ${\mathrm{MnPt}}_{3},$ ${\mathrm{Fe}}_{3}\mathrm{Pt}$ and ${\mathrm{CoPt}}_{3}.$ The electronic state, especially the contribution of the spin and orbital angular momenta to the magnetic moment, is discussed by analyzing the results. The condition for the orbital angular momentum to make a large contribution to the magnetic moment in a metallic system is discussed in terms of the degree of the localization of the $3d$ orbital, the filling of it, and the symmetry around it.