Multiscale Characterisation and Modelling of Grain Junctions in Nd-Fe-B Sintered Magnets

摘要

Aberration-corrected transmission electron microscopy combined with atomistic simulations has been used to study the structure of the interface between Nd_2Fe_(14)B and Nd oxide phases in Nd-Fe-B sintered magnets on the atomic scale. The Nd-oxide grains have interfaces with several Nd_2Fe_(14)B grains and therefore the magnetisation reversal behaviour of such ensembles of grains is of interest. Electron backscatter diffraction and energy dispersive x-ray spectroscopy have been used to identify the phases, crystal orientations and grain boundary geometry of typical grain junctions. This information combined with that gained from atomistic simulations of individual interfaces has been used as input for finite element micromagnetic simulations of reversal in the grain ensembles. The results showed different coercive fields for two different crystal structures of Nd_2O_3, indicating that some Nd-oxide phases may have a more detrimental effect on coercivity than others.