Synthesis, Crystallographic, and Magnetic Properties of Interstitial and Substitutional Hard Magnetic Materials

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9521739 Long The goal of this project is to learn how to produce practical magnets based on R2Fel7 materials by adding a combination of substitutional and interstitial elements. The proposed work involves both synthesis and characterization studies using magnetic, neutron diffraction, and Mossbauer spectroscopies. Samples will be prepared by arc or induction melting, followed by annealing. Magnetic measurements will be used to determine the bulk magnetic properties of the resulting materials. Rietveld refinement of neutron diffraction data will be used to determine the crystallo- graphic and magnetic properties of the materials, including site occupancies of the substitutional and interstitial elements and the magnetic moments at each magnetic atom site. Mossbauer spectral analysis will be used to obtain detailed microscopic information about the magnetic properties and local electronic environment at each iron site. A Wigner-Seitz cell analysis of each crystallographic site will be used to determine the relationship between the site's microscopic crystallographic and magnetic properties and the corresponding bulk properties of the magnets. %%% The discovery in the early 1980's of the rare earth-iron- boron magnets revolutionized the permanent magnet industry. These materials offered a significant improvement in magnetic properties over the previous best permanent magnetic materials, at about half the cost in terms of energy stored per unit mass of material. However, the Curie temperature of the rare earth-iron-boron magnets is less than 60% of the Curie temperature of the previous best permanent magnets. Substitutional additions unfortunately did not substantially increase the highest Curie temperature of the compounds and their practical utility. The goal of this project is to learn how to make practical magnets based on R2Fel7 materials by the addition of a combination of substitutional and interstitial elements. The right combina- tion of elements sho uld greatly improve the thermomagnetic properties of such materials. ***