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Electronic Origin of Delicate Antiferromagnetism in Fe 𝑥 NbS 2
Among the family of intercalated transition-metal dichalcogenides (TMDs), Fe 𝑥 NbS 2 is found to possess unique current-induced resistive switching behaviors, tunable antiferromagnetic states, and a commensurate charge order, all of which are tied to a critical Fe doping of 𝑥 𝑐 = 1/3. However, the electronic origin of such extreme stoichiometry sensitivities remains unclear. Combining angle-resolved photoemission spectroscopy (ARPES) with density functional theory (DFT) calculations, we identify and characterize a dramatic eV-scale electronic restructuring that occurs across the 𝑥𝑐. Moment-carrying Fe 3𝑑 𝑧 2 electrons manifest as narrow bands within 200 meV of the Fermi level, distinct from other transition metal intercalated TMD magnets. These states strongly hybridize with itinerant electrons in the TMD layer and rapidly lose coherence above 𝑥 𝑐 due to correlation-driven effects. This sudden quasiparticle decoherence collapses the Fe-Nb hybridization, which explicitly suppresses the out-of-plane effective Fe-Fe exchange interaction, driving the transformation of the magnetic ground state from an antiferromagnetic stripe phase to a zigzag phase. Furthermore, these observations resemble the exceptional electronic and magnetic sensitivity of strongly correlated systems, and demonstrate that quantifying orbital-specific hybridization via ARPES offers an alternative pathway to evaluate effective magnetic exchange in metallic magnets, complementing inelastic neutron and resonant x-ray scattering probes.
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.
Materials Data on NbFe2 by Materials Project
Fe2Nb is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Nb is bonded in a 12-coordinate geometry to four equivalent Nb and twelve Fe atoms. There are one shorter (2.91 Å) and three longer (2.95 Å) Nb–Nb bond lengths. There are a spread of Nb–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 Nb and six equivalent Fe atoms to form a mixture of corner, edge, and face-sharing FeNb6Fe6 cuboctahedra. All Fe–Fe bond lengths are 2.43 Å. In the second Fe site, Fe is bonded to six equivalent Nb and six Fe atoms to form a mixture of corner, edge, and face-sharing FeNb6Fe6 cuboctahedra. There are two shorter (2.34 Å) and two longer (2.44 Å) Fe–Fe bond lengths.
Materials Data on NbFe3 by Materials Project
Fe3Nb is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Nb is bonded in a distorted body-centered cubic geometry to fourteen Fe atoms. There are eight shorter (2.56 Å) and six longer (2.96 Å) Nb–Fe bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted body-centered cubic geometry to four equivalent Nb and four equivalent Fe atoms. All Fe–Fe bond lengths are 2.56 Å. In the second Fe site, Fe is bonded in a 8-coordinate geometry to six equivalent Nb and eight equivalent Fe atoms.
Materials Data on NbFe3 by Materials Project
Fe3Nb is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Nb is bonded to twelve Fe atoms to form NbFe12 cuboctahedra that share corners with four equivalent NbFe12 cuboctahedra, edges with eight equivalent NbFe12 cuboctahedra, edges with sixteen equivalent FeNb4Fe8 cuboctahedra, faces with four equivalent NbFe12 cuboctahedra, and faces with eight equivalent FeNb4Fe8 cuboctahedra. There are four shorter (2.53 Å) and eight longer (2.73 Å) Nb–Fe bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted square co-planar geometry to four equivalent Nb and eight equivalent Fe atoms. All Fe–Fe bond lengths are 2.73 Å. In the second Fe site, Fe is bonded to four equivalent Nb and eight Fe atoms to form FeNb4Fe8 cuboctahedra that share corners with twelve equivalent FeNb4Fe8 cuboctahedra, edges with eight equivalent NbFe12 cuboctahedra, edges with eight equivalent FeNb4Fe8 cuboctahedra, faces with four equivalent NbFe12 cuboctahedra, and faces with ten equivalent FeNb4Fe8 cuboctahedra. All Fe–Fe bond lengths are 2.53 Å.
Materials Data on Nb3Fe by Materials Project
Nb3Fe is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Nb sites. In the first Nb site, Nb is bonded in a square co-planar geometry to eight equivalent Nb and four equivalent Fe atoms. All Nb–Nb bond lengths are 2.99 Å. All Nb–Fe bond lengths are 2.68 Å. In the second Nb site, Nb is bonded to eight Nb and four equivalent Fe atoms to form NbNb8Fe4 cuboctahedra that share corners with twelve equivalent NbNb8Fe4 cuboctahedra, edges with eight equivalent NbNb8Fe4 cuboctahedra, edges with eight equivalent FeNb12 cuboctahedra, faces with four equivalent FeNb12 cuboctahedra, and faces with ten equivalent NbNb8Fe4 cuboctahedra. All Nb–Nb bond lengths are 2.68 Å. All Nb–Fe bond lengths are 2.99 Å. Fe is bonded to twelve Nb atoms to form FeNb12 cuboctahedra that share corners with four equivalent FeNb12 cuboctahedra, edges with eight equivalent FeNb12 cuboctahedra, edges with sixteen equivalent NbNb8Fe4 cuboctahedra, faces with four equivalent FeNb12 cuboctahedra, and faces with eight equivalent NbNb8Fe4 cuboctahedra.
Materials Data on NbFe2 by Materials Project
Fe2Nb is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Nb is bonded in a 12-coordinate geometry to four equivalent Nb and twelve equivalent Fe atoms. All Nb–Nb bond lengths are 2.95 Å. All Nb–Fe bond lengths are 2.83 Å. Fe is bonded to six equivalent Nb and six equivalent Fe atoms to form a mixture of edge, face, and corner-sharing FeNb6Fe6 cuboctahedra. All Fe–Fe bond lengths are 2.41 Å.
Materials Data on NbFe by Materials Project
FeNb 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 Nb sites. In the first Nb site, Nb is bonded in a 10-coordinate geometry to seven Nb and nine equivalent Fe atoms. There are a spread of Nb–Nb bond distances ranging from 2.80–2.96 Å. There are three shorter (2.90 Å) and six longer (3.00 Å) Nb–Fe bond lengths. In the second Nb site, Nb is bonded in a 6-coordinate geometry to four Nb and twelve Fe atoms. There are one shorter (2.72 Å) and three longer (2.95 Å) Nb–Nb bond lengths. There are a spread of Nb–Fe bond distances ranging from 2.76–2.93 Å. In the third Nb site, Nb is bonded in a 8-coordinate geometry to eight Nb and six equivalent Fe atoms. There are one shorter (2.64 Å) and six longer (3.14 Å) Nb–Nb bond lengths. All Nb–Fe bond lengths are 2.69 Å. In the fourth Nb site, Nb is bonded in a 8-coordinate geometry to eight Nb and six equivalent Fe atoms. All Nb–Nb bond lengths are 3.13 Å. All Nb–Fe bond lengths are 2.71 Å. In the fifth Nb site, Nb is bonded in a 6-coordinate geometry to nine Nb and six Fe atoms. All Nb–Nb bond lengths are 2.84 Å. All Nb–Fe bond lengths are 2.82 Å. In the sixth Nb site, Nb is bonded in a 6-coordinate geometry to nine Nb and six Fe atoms. There are three shorter (2.78 Å) and three longer (2.83 Å) Nb–Fe bond lengths. In the seventh Nb site, Nb is bonded to six equivalent Nb and six equivalent Fe atoms to form distorted NbNb6Fe6 cuboctahedra that share corners with twelve equivalent FeNb8Fe4 cuboctahedra, edges with six equivalent NbNb6Fe6 cuboctahedra, and faces with eighteen equivalent FeNb8Fe4 cuboctahedra. All Nb–Fe bond lengths are 2.57 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded to seven Nb and five Fe atoms to form FeNb7Fe5 cuboctahedra that share corners with fifteen FeNb7Fe5 cuboctahedra, edges with five FeNb8Fe4 cuboctahedra, and faces with thirteen FeNb7Fe5 cuboctahedra. There are one shorter (2.44 Å) and four longer (2.46 Å) Fe–Fe bond lengths. In the second Fe site, Fe is bonded to eight Nb and four equivalent Fe atoms to form distorted FeNb8Fe4 cuboctahedra that share corners with two equivalent NbNb6Fe6 cuboctahedra, corners with thirteen FeNb7Fe5 cuboctahedra, edges with five FeNb8Fe4 cuboctahedra, faces with three equivalent NbNb6Fe6 cuboctahedra, and faces with ten equivalent FeNb8Fe4 cuboctahedra. There are two shorter (2.41 Å) and two longer (2.52 Å) Fe–Fe bond lengths. In the third Fe site, Fe is bonded to six equivalent Nb and six equivalent Fe atoms to form FeNb6Fe6 cuboctahedra that share corners with twelve equivalent FeNb7Fe5 cuboctahedra, edges with six equivalent FeNb6Fe6 cuboctahedra, and faces with eighteen equivalent FeNb7Fe5 cuboctahedra.
Materials Data on Nb19Fe20 by Materials Project
Nb19Fe20 is Frank-Kasper $\mu$ Phase-like structured and crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are ten inequivalent Nb sites. In the first Nb site, Nb is bonded in a 8-coordinate geometry to eight Nb and six equivalent Fe atoms. There are a spread of Nb–Nb bond distances ranging from 2.65–3.13 Å. All Nb–Fe bond lengths are 2.71 Å. In the second Nb site, Nb is bonded in a 8-coordinate geometry to eight Nb and six equivalent Fe atoms. There are a spread of Nb–Nb bond distances ranging from 2.65–3.14 Å. All Nb–Fe bond lengths are 2.71 Å. In the third Nb site, Nb is bonded in a 8-coordinate geometry to eight Nb and six equivalent Fe atoms. There are one shorter (2.77 Å) and six longer (3.15 Å) Nb–Nb bond lengths. All Nb–Fe bond lengths are 2.69 Å. In the fourth Nb site, Nb is bonded in a 6-coordinate geometry to nine Nb and six Fe atoms. All Nb–Nb bond lengths are 2.85 Å. There are three shorter (2.78 Å) and three longer (2.81 Å) Nb–Fe bond lengths. In the fifth Nb site, Nb is bonded in a 9-coordinate geometry to nine Nb and six equivalent Fe atoms. All Nb–Nb bond lengths are 2.85 Å. All Nb–Fe bond lengths are 2.84 Å. In the sixth Nb site, Nb is bonded in a 6-coordinate geometry to nine Nb and six Fe atoms. There are three shorter (2.81 Å) and three longer (2.82 Å) Nb–Fe bond lengths. In the seventh Nb site, Nb is bonded in a 6-coordinate geometry to four Nb and twelve Fe atoms. All Nb–Nb bond lengths are 2.94 Å. There are a spread of Nb–Fe bond distances ranging from 2.79–2.96 Å. In the eighth Nb site, Nb is bonded in a 6-coordinate geometry to four Nb and twelve Fe atoms. There are a spread of Nb–Fe bond distances ranging from 2.78–2.97 Å. In the ninth Nb site, Nb is bonded in a 10-coordinate geometry to seven Nb and nine equivalent Fe atoms. There are three shorter (2.88 Å) and three longer (2.97 Å) Nb–Nb bond lengths. There are three shorter (2.91 Å) and six longer (3.00 Å) Nb–Fe bond lengths. In the tenth Nb site, Nb is bonded to six equivalent Nb and six equivalent Fe atoms to form distorted NbNb6Fe6 cuboctahedra that share corners with twelve equivalent FeNb8Fe4 cuboctahedra, edges with six equivalent NbNb6Fe6 cuboctahedra, and faces with eighteen equivalent FeNb8Fe4 cuboctahedra. All Nb–Fe bond lengths are 2.58 Å. There are four inequivalent Fe sites. In the first Fe site, Fe is bonded to six Nb and six Fe atoms to form FeNb6Fe6 cuboctahedra that share corners with twelve FeNb7Fe5 cuboctahedra, edges with six equivalent FeNb6Fe6 cuboctahedra, and faces with eighteen FeNb7Fe5 cuboctahedra. All Fe–Fe bond lengths are 2.47 Å. In the second Fe site, Fe is bonded to eight Nb and four equivalent Fe atoms to form distorted FeNb8Fe4 cuboctahedra that share corners with two equivalent NbNb6Fe6 cuboctahedra, corners with thirteen FeNb8Fe4 cuboctahedra, edges with five FeNb8Fe4 cuboctahedra, faces with three equivalent NbNb6Fe6 cuboctahedra, and faces with ten equivalent FeNb8Fe4 cuboctahedra. There are two shorter (2.41 Å) and two longer (2.52 Å) Fe–Fe bond lengths. In the third Fe site, Fe is bonded to seven Nb and five Fe atoms to form FeNb7Fe5 cuboctahedra that share corners with fifteen FeNb6Fe6 cuboctahedra, edges with five FeNb7Fe5 cuboctahedra, and faces with thirteen FeNb6Fe6 cuboctahedra. There are two shorter (2.46 Å) and two longer (2.47 Å) Fe–Fe bond lengths. In the fourth Fe site, Fe is bonded to seven Nb and five Fe atoms to form FeNb7Fe5 cuboctahedra that share corners with fifteen FeNb6Fe6 cuboctahedra, edges with five FeNb8Fe4 cuboctahedra, and faces with thirteen FeNb6Fe6 cuboctahedra. There are two shorter (2.46 Å) and two longer (2.47 Å) Fe–Fe bond lengths.
Materials Data on NbFe3 by Materials Project
Fe3Nb is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Nb is bonded to twelve equivalent Fe atoms to form NbFe12 cuboctahedra that share corners with twelve equivalent NbFe12 cuboctahedra, edges with twenty-four equivalent FeNb4Fe8 cuboctahedra, faces with six equivalent NbFe12 cuboctahedra, and faces with twelve equivalent FeNb4Fe8 cuboctahedra. All Nb–Fe bond lengths are 2.64 Å. Fe is bonded to four equivalent Nb and eight equivalent Fe atoms to form FeNb4Fe8 cuboctahedra that share corners with twelve equivalent FeNb4Fe8 cuboctahedra, edges with eight equivalent NbFe12 cuboctahedra, edges with sixteen equivalent FeNb4Fe8 cuboctahedra, faces with four equivalent NbFe12 cuboctahedra, and faces with fourteen equivalent FeNb4Fe8 cuboctahedra. All Fe–Fe bond lengths are 2.64 Å.