Anisotropy and microstructure of rare-earth permanent-magnet materials. Final report, December 1083-March 1986

This report is divided into two parts, the microstructural investigations and the anisotropy measurements of rare-earth permanent-magnet materials. Section I shows that the hard magnetic properties, i.e. coercivity, of the individual Nd-Fe-B permanent magnet material strongly depends on the compositional and processing parameters (milling, blending, annealing, etc.) and are directly correlated to the microstructural properties (grain size, composition and distribution of phases, crystal defects and precipitates) and to the magnetocrystalline anisotropy of the material. By means of transmission electron microscopy together with STEM x-ray microanalysis, at least three categories of phases were identified in sintered rare earth-iron permanent magnets. From microstructural investigations it can be assumed that the coercivity of sintered rare earth-iron permanent magnet materials is controlled by the nucleation and expansion fields for reversed domains. In Section II the magnetic anisotropy measurements of various rare earth-iron based magnets between 80 K and the Curie temperature are shown and the results are discussed by means of a expanded model for the anisotropy field. From the study of the temperature dependence of the anisotropy field of the mixed crystal series (N,RE)15Fe77B8 (RE=Y, La, Ce) the ine ion character of the Nd sublattice is shown.