MAGNETIC-STRUCTURE DETERMINATION OF AMORPHOUS MATERIALS USING RMC MODELING OF NEUTRON-DIFFRACTION DATA

Several difficulties arise when attempting to interpret diffraction da ta from amorphous magnetic materials. These are due to the increased c omplexity of the measured structure factors which contain magnetic and nuclear components. In order to determine the magnetic structure from these data it is necessary to isolate the magnetic contribution and u se this to produce a satisfactory spin distribution model. This model also relies on information about the disordered nuclear structure. In principle therefore, one data set must yield sufficient information to describe both the disordered atomic and magnetic structure. To compli cate things further it is usually not possible to directly transform a magnetic structure factor to a real space spin-spin correlation funct ion in a manner analogous to the production of an atomic radial distri bution function from an atomic structure factor. Reverse Monte Carlo ( RMC) modelling has been established over the past few years as a metho d for deducing disordered atomic structures from diffraction data. Thi s paper introduces its application to disordered magnetic systems. Usi ng the family of amorphous magnetic alloys (Dy, Y)(7)Ni-3, as an examp le, it is demonstrated that RMC can produce three-dimensional spin dis tributions from structure factor data with remarkably consistent magne tic characteristics.