Magnetic structure determination of amorphous materials using RMC modelling of neutron diffraction data

Several difficulties arise when attempting to interpret diffraction data from amorphous magnetic materials. These are due to the increased complexity 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 use 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 complicate things further it is usually not possible to directly transform a magnetic structure factor to a real space spin-spin correlation function in a manner analogous to the production of an atomic radial distribution function from an atomic structure factor. Reverse Monte Carlo (RMC) modelling has been established over the past few years as a method for deducing disordered atomic structures from diffraction data. This paper introduces its application to disordered magnetic systems. Using the family of amorphous magnetic alloys (Dy, Y)7Ni3 as an example, it is demonstrated that RMC can produce three-dimensional spin distributions from structure factor data with remarkably consistent magnetic characteristics.