ITINERANT MAGNETISM OF DISORDERED FE-CO AND NI-CU ALLOYS IN 2-DIMENSIONS AND 3-DIMENSIONS

The electronic structure and band magnetism of disordered Fe100-xCox a nd Ni100-xCux bulk alloys and of corresponding disordered overlayers o n an fee Cu(001) substrate were studied by means of the first-principl es tight-binding linear muffin-tin orbital coherent potential approxim ation method. For the Fe-Co system, we found that the composition depe ndence of the averaged and the local Fe magnetic moments is strongly a ffected by the dimensionality of the system while the local Co moments remain nearly constant. In the bulk bcc alloys, a nonmonotonic behavi or of the averaged magnetization occurs due to the transition from wea k to strong ferromagnetism. The averaged magnetization of the random o verlayers depends linearly on the composition while the local Fe and C o moments are constant since the strong ferromagnetism is stabilized b y the substrate throughout the whole composition range. For the Ni-Cu system, a transition from ferromagnetism to paramagnetism is found bot h in the bulk fee alloys and in the overlayers. The ferromagnetism of the overlayers is reduced in comparison to the bulk systems of the sam e composition. The concentration trends of local densities of states, local numbers of electrons, and work functions are discussed.