Effect of topological disorder on the itinerant magnetism of Fe and Co

Theoretical investigations of the magnetic properties of amorphous Fe and Co have been carried out using linear muffin-tin orbital Green’s-function (LMTO-GF) and LMTO-recursion methods. The differences in the effect of topological disorder on the magnetic behavior of Fe and Co are studied via self-consistent calculations of local magnetic moments (LMM’s) and effective exchange interaction parameters (EEIP) in 64- and 600-atom model clusters, generated by the Monte Carlo method. Analytical expressions for EEIP’s, obtained in the framework of the density-functional theory within the local-density approximation using a local ‘‘force’’ theorem, are evaluated in the LMTO basis. An interpretation of the effect of disorder on the magnetic behavior of Fe and Co is provided, based on a study of the volume dependence of magnetic moment and exchange interaction in the fcc phase and the distribution of LMM’s, EEIP’s, Voronoi polyhedra volumes, and other local symmetry parameters in the amorphous phase. By examining the interrelations among these quantities we isolate important local and global structural characteristics dictating the idiosyncrasies of magnetism in these two amorphous metals.