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4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Electronic Structure and Spin Correlations in Novel Magnetic Structures

The research has advanced understanding of the interrelation between the crystal structure and magnetism in several materials which are or can be of interest for the development of improved, specialized or more cost-effective permanent magnets, as well as in selected materials for biomedical and catalytic applications. Fundamental aspects of ferromagnetism were investigated for Mn-Ge, Co-V and Co-Ge nanoclusters and for melt-spun Co-Sn alloys. New solution-chemistry synthesis methods were designed and tested for Fe-Pt, Fe3C and Fe3O4 nanoparticles. Off-stoichiometric Laves phases in the Fe-Si-Zr, Fe-Nb and Fe-Ta systems, as well as Fe5(Si,Ge)B2 compounds were assessed as new rare-earth-free permanent magnet materials; all except the Fe-Si-Zr Laves phases were found to be promising enough to merit a further exploration. A new method for manufacturing rare-earth-free magnets based on the MnBi compound was developed; by purposely avoiding oxidation-sensitive fine single-crystalline powders, the new method yields magnets with a 50% larger energy storage capacity. Studies of rare-earth-lean permanent-magnet materials (lean compared to the currently predominant Nd-Fe-B materials) were focused on the tetragonal compound of the ThMn12 structure type and included both discovery and characterization of new formulations and exploration of new fabrication/processing techniques. Among the most significant achievements were successful preparation of a vanadium-lean SmFe11V compound, the first observation of thermomechanically induced texture in nanocrystalline Sm(Fe,V)12 alloys, and a breakthrough reduction-diffusion synthesis of Sm1-xZrx(Fe0.8Co0.2)11.2Ti0.8 single-crystal particles with a coercivity as high as 12.6 kOe. Several experiments aimed at improvement of the Nd-Fe-B magnet have also been undertaken including a five-fold increase of the coercivity through a grain-boundary diffusion treatment of a Nd10Fe84B6 nanocrystalline alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaFe2 by Materials Project

TaFe2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve Fe atoms. There are one shorter (2.91 Å) and three longer (2.95 Å) Ta–Ta bond lengths. There are a spread of Ta–Fe bond distances ranging from 2.80–2.84 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six equivalent Ta and six equivalent Fe atoms to form a mixture of edge, face, and corner-sharing FeTa6Fe6 cuboctahedra. All Fe–Fe bond lengths are 2.42 Å. In the second Fe site, Fe is bonded to six equivalent Ta and six Fe atoms to form a mixture of edge, face, and corner-sharing FeTa6Fe6 cuboctahedra. There are two shorter (2.37 Å) and two longer (2.41 Å) Fe–Fe bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaFe by Materials Project

FeTa is Frank-Kasper $\mu$ Phase-like structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are seven inequivalent Ta sites. In the first Ta site, Ta is bonded in a 6-coordinate geometry to eight Ta and six equivalent Fe atoms. There are a spread of Ta–Ta bond distances ranging from 2.66–3.12 Å. All Ta–Fe bond lengths are 2.66 Å. In the second Ta site, Ta is bonded in a 8-coordinate geometry to eight Ta and six equivalent Fe atoms. There are a spread of Ta–Ta bond distances ranging from 2.76–3.11 Å. All Ta–Fe bond lengths are 2.68 Å. In the third Ta site, Ta is bonded in a 9-coordinate geometry to seven Ta and nine equivalent Fe atoms. There are three shorter (2.84 Å) and three longer (2.91 Å) Ta–Ta bond lengths. There are three shorter (2.83 Å) and six longer (2.99 Å) Ta–Fe bond lengths. In the fourth Ta site, Ta is bonded in a 12-coordinate geometry to four Ta and twelve Fe atoms. All Ta–Ta bond lengths are 2.91 Å. There are a spread of Ta–Fe bond distances ranging from 2.77–2.93 Å. In the fifth Ta site, Ta is bonded in a 6-coordinate geometry to nine Ta and six Fe atoms. All Ta–Ta bond lengths are 2.81 Å. There are three shorter (2.79 Å) and three longer (2.83 Å) Ta–Fe bond lengths. In the sixth Ta site, Ta is bonded in a 6-coordinate geometry to nine Ta and six Fe atoms. There are three shorter (2.78 Å) and three longer (2.82 Å) Ta–Fe bond lengths. In the seventh Ta site, Ta is bonded to six equivalent Ta and six equivalent Fe atoms to form distorted TaTa6Fe6 cuboctahedra that share corners with twelve equivalent FeTa8Fe4 cuboctahedra, edges with six equivalent TaTa6Fe6 cuboctahedra, and faces with eighteen equivalent FeTa8Fe4 cuboctahedra. All Ta–Fe bond lengths are 2.55 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded to seven Ta and five Fe atoms to form FeTa7Fe5 cuboctahedra that share corners with fifteen FeTa7Fe5 cuboctahedra, edges with five FeTa8Fe4 cuboctahedra, and faces with thirteen FeTa7Fe5 cuboctahedra. There are a spread of Fe–Fe bond distances ranging from 2.42–2.46 Å. In the second Fe site, Fe is bonded to eight Ta and four equivalent Fe atoms to form distorted FeTa8Fe4 cuboctahedra that share corners with two equivalent TaTa6Fe6 cuboctahedra, corners with thirteen FeTa7Fe5 cuboctahedra, edges with five FeTa8Fe4 cuboctahedra, faces with three equivalent TaTa6Fe6 cuboctahedra, and faces with ten equivalent FeTa8Fe4 cuboctahedra. There are two shorter (2.38 Å) and two longer (2.49 Å) Fe–Fe bond lengths. In the third Fe site, Fe is bonded to six equivalent Ta and six equivalent Fe atoms to form FeTa6Fe6 cuboctahedra that share corners with twelve equivalent FeTa7Fe5 cuboctahedra, edges with six equivalent FeTa6Fe6 cuboctahedra, and faces with eighteen equivalent FeTa7Fe5 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2Fe by Materials Project

Ta2Fe crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are six inequivalent Ta sites. In the first Ta site, Ta is bonded to six Ta and six equivalent Fe atoms to form distorted TaTa6Fe6 cuboctahedra that share corners with eighteen equivalent FeTa9Fe3 cuboctahedra, edges with eighteen TaTa6Fe6 cuboctahedra, faces with six equivalent FeTa9Fe3 cuboctahedra, and faces with fourteen TaTa6Fe6 cuboctahedra. There are two shorter (2.91 Å) and four longer (2.92 Å) Ta–Ta bond lengths. There are four shorter (2.80 Å) and two longer (2.82 Å) Ta–Fe bond lengths. In the second Ta site, Ta is bonded to eight Ta and four equivalent Fe atoms to form distorted TaTa8Fe4 cuboctahedra that share corners with twelve TaTa8Fe4 cuboctahedra, edges with eight equivalent FeTa9Fe3 cuboctahedra, edges with sixteen TaTa6Fe6 cuboctahedra, faces with eight equivalent FeTa9Fe3 cuboctahedra, and faces with ten TaTa6Fe6 cuboctahedra. There are a spread of Ta–Ta bond distances ranging from 2.76–2.88 Å. All Ta–Fe bond lengths are 2.88 Å. In the third Ta site, Ta is bonded to eight Ta and four equivalent Fe atoms to form distorted TaTa8Fe4 cuboctahedra that share corners with twelve TaTa8Fe4 cuboctahedra, edges with eight equivalent FeTa9Fe3 cuboctahedra, edges with sixteen TaTa6Fe6 cuboctahedra, faces with eight equivalent FeTa9Fe3 cuboctahedra, and faces with ten TaTa6Fe6 cuboctahedra. There are a spread of Ta–Ta bond distances ranging from 2.76–2.92 Å. All Ta–Fe bond lengths are 2.88 Å. In the fourth Ta site, Ta is bonded to eight Ta and four equivalent Fe atoms to form distorted TaTa8Fe4 cuboctahedra that share corners with twelve TaTa8Fe4 cuboctahedra, edges with eight equivalent FeTa9Fe3 cuboctahedra, edges with sixteen TaTa6Fe6 cuboctahedra, faces with eight equivalent FeTa9Fe3 cuboctahedra, and faces with ten TaTa6Fe6 cuboctahedra. The Ta–Ta bond length is 2.90 Å. All Ta–Fe bond lengths are 2.88 Å. In the fifth Ta site, Ta is bonded to eight Ta and four equivalent Fe atoms to form distorted TaTa8Fe4 cuboctahedra that share corners with twelve TaTa8Fe4 cuboctahedra, edges with eight equivalent FeTa9Fe3 cuboctahedra, edges with sixteen TaTa6Fe6 cuboctahedra, faces with eight equivalent FeTa9Fe3 cuboctahedra, and faces with ten TaTa6Fe6 cuboctahedra. There are two shorter (2.76 Å) and one longer (2.90 Å) Ta–Ta bond lengths. All Ta–Fe bond lengths are 2.88 Å. In the sixth Ta site, Ta is bonded to eight Ta and four equivalent Fe atoms to form distorted TaTa8Fe4 cuboctahedra that share corners with twelve TaTa8Fe4 cuboctahedra, edges with eight equivalent FeTa9Fe3 cuboctahedra, edges with sixteen TaTa6Fe6 cuboctahedra, faces with eight equivalent FeTa9Fe3 cuboctahedra, and faces with ten TaTa6Fe6 cuboctahedra. There are a spread of Ta–Ta bond distances ranging from 2.76–2.92 Å. All Ta–Fe bond lengths are 2.88 Å. Fe is bonded to nine Ta and three equivalent Fe atoms to form distorted FeTa9Fe3 cuboctahedra that share corners with nine equivalent TaTa6Fe6 cuboctahedra, corners with nine equivalent FeTa9Fe3 cuboctahedra, edges with six equivalent FeTa9Fe3 cuboctahedra, edges with twelve TaTa8Fe4 cuboctahedra, faces with five equivalent FeTa9Fe3 cuboctahedra, and faces with fifteen TaTa6Fe6 cuboctahedra. There are two shorter (2.80 Å) and one longer (2.83 Å) Fe–Fe bond lengths.

36 MATERIALS SCIENCE↗