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30 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Zr(FeSn)6 by Materials Project

Fe6Sn6Zr crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Zr is bonded to twelve equivalent Fe and eight Sn atoms to form distorted face-sharing ZrFe12Sn8 hexagonal bipyramids. All Zr–Fe bond lengths are 3.47 Å. There are two shorter (2.98 Å) and six longer (3.10 Å) Zr–Sn bond lengths. Fe is bonded in a 12-coordinate geometry to two equivalent Zr, four equivalent Fe, and six Sn atoms. All Fe–Fe bond lengths are 2.69 Å. There are a spread of Fe–Sn bond distances ranging from 2.69–2.79 Å. There are three inequivalent Sn sites. In the first Sn site, Sn is bonded in a 8-coordinate geometry to one Zr, six equivalent Fe, and one Sn atom. The Sn–Sn bond length is 2.94 Å. In the second Sn site, Sn is bonded in a 12-coordinate geometry to three equivalent Zr and six equivalent Fe atoms. In the third Sn site, Sn is bonded in a 6-coordinate geometry to six equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(FeSn)6 by Materials Project

LuFe6Sn6 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Lu is bonded to twelve equivalent Fe and eight Sn atoms to form distorted LuFe12Sn8 hexagonal bipyramids that share faces with twenty-four equivalent FeLu2Fe4Sn6 cuboctahedra and faces with six equivalent LuFe12Sn8 hexagonal bipyramids. All Lu–Fe bond lengths are 3.48 Å. There are two shorter (3.01 Å) and six longer (3.12 Å) Lu–Sn bond lengths. Fe is bonded to two equivalent Lu, four equivalent Fe, and six Sn atoms to form distorted FeLu2Fe4Sn6 cuboctahedra that share corners with fourteen equivalent FeLu2Fe4Sn6 cuboctahedra, edges with seven equivalent FeLu2Fe4Sn6 cuboctahedra, faces with nine equivalent FeLu2Fe4Sn6 cuboctahedra, and faces with four equivalent LuFe12Sn8 hexagonal bipyramids. All Fe–Fe bond lengths are 2.71 Å. There are a spread of Fe–Sn bond distances ranging from 2.69–2.83 Å. There are three inequivalent Sn sites. In the first Sn site, Sn is bonded in a 12-coordinate geometry to three equivalent Lu and six equivalent Fe atoms. In the second Sn site, Sn is bonded in a 6-coordinate geometry to six equivalent Fe atoms. In the third Sn site, Sn is bonded in a 8-coordinate geometry to one Lu, six equivalent Fe, and one Sn atom. The Sn–Sn bond length is 2.92 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(FeSn)6 by Materials Project

TmFe6Sn6 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Tm is bonded to twelve equivalent Fe and eight Sn atoms to form distorted TmFe12Sn8 hexagonal bipyramids that share faces with twenty-four equivalent FeTm2Fe4Sn6 cuboctahedra and faces with six equivalent TmFe12Sn8 hexagonal bipyramids. All Tm–Fe bond lengths are 3.48 Å. There are two shorter (3.00 Å) and six longer (3.12 Å) Tm–Sn bond lengths. Fe is bonded to two equivalent Tm, four equivalent Fe, and six Sn atoms to form distorted FeTm2Fe4Sn6 cuboctahedra that share corners with fourteen equivalent FeTm2Fe4Sn6 cuboctahedra, edges with seven equivalent FeTm2Fe4Sn6 cuboctahedra, faces with nine equivalent FeTm2Fe4Sn6 cuboctahedra, and faces with four equivalent TmFe12Sn8 hexagonal bipyramids. All Fe–Fe bond lengths are 2.71 Å. There are a spread of Fe–Sn bond distances ranging from 2.69–2.82 Å. There are three inequivalent Sn sites. In the first Sn site, Sn is bonded in a 12-coordinate geometry to three equivalent Tm and six equivalent Fe atoms. In the second Sn site, Sn is bonded in a 6-coordinate geometry to six equivalent Fe atoms. In the third Sn site, Sn is bonded in a 8-coordinate geometry to one Tm, six equivalent Fe, and one Sn atom. The Sn–Sn bond length is 2.91 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(FeSn)6 by Materials Project

YFe6Sn6 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded to twelve Fe and eight Sn atoms to form distorted YFe12Sn8 hexagonal bipyramids that share faces with eight FeY2Fe4Sn6 cuboctahedra and faces with six YFe12Sn8 hexagonal bipyramids. There are four shorter (3.49 Å) and eight longer (3.51 Å) Y–Fe bond lengths. There are a spread of Y–Sn bond distances ranging from 3.02–3.17 Å. In the second Y site, Y is bonded to twelve Fe and eight Sn atoms to form distorted YFe12Sn8 hexagonal bipyramids that share corners with four equivalent YFe12Sn8 hexagonal bipyramids, faces with sixteen FeY2Fe4Sn6 cuboctahedra, and faces with four YFe12Sn8 hexagonal bipyramids. There are a spread of Y–Fe bond distances ranging from 3.49–3.53 Å. There are a spread of Y–Sn bond distances ranging from 3.03–3.17 Å. There are four inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Y, four equivalent Fe, and six Sn atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with six FeY2Fe4Sn6 cuboctahedra, edges with three equivalent FeY2Fe4Sn6 cuboctahedra, a faceface with one FeY2Fe4Sn6 cuboctahedra, and faces with four YFe12Sn8 hexagonal bipyramids. All Fe–Fe bond lengths are 2.72 Å. There are a spread of Fe–Sn bond distances ranging from 2.72–2.82 Å. In the second Fe site, Fe is bonded to two equivalent Y, four Fe, and six Sn atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with eight FeY2Fe4Sn6 cuboctahedra, edges with four FeY2Fe4Sn6 cuboctahedra, faces with eight FeY2Fe4Sn6 cuboctahedra, and faces with four equivalent YFe12Sn8 hexagonal bipyramids. There are two shorter (2.70 Å) and two longer (2.72 Å) Fe–Fe bond lengths. There are a spread of Fe–Sn bond distances ranging from 2.73–2.83 Å. In the third Fe site, Fe is bonded to two equivalent Y, four Fe, and six Sn atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with ten FeY2Fe4Sn6 cuboctahedra, edges with five FeY2Fe4Sn6 cuboctahedra, faces with five FeY2Fe4Sn6 cuboctahedra, and faces with four YFe12Sn8 hexagonal bipyramids. Both Fe–Fe bond lengths are 2.70 Å. There are a spread of Fe–Sn bond distances ranging from 2.71–2.82 Å. In the fourth Fe site, Fe is bonded in a 12-coordinate geometry to two Y, four Fe, and six Sn atoms. There are one shorter (2.70 Å) and one longer (2.71 Å) Fe–Fe bond lengths. There are a spread of Fe–Sn bond distances ranging from 2.71–2.83 Å. There are nine inequivalent Sn sites. In the first Sn site, Sn is bonded in a 8-coordinate geometry to one Y, six Fe, and one Sn atom. Both Sn–Fe bond lengths are 2.82 Å. The Sn–Sn bond length is 2.95 Å. In the second Sn site, Sn is bonded in a 6-coordinate geometry to six Fe atoms. In the third Sn site, Sn is bonded in a 12-coordinate geometry to three Y and six Fe atoms. In the fourth Sn site, Sn is bonded in a 8-coordinate geometry to two equivalent Y and six Fe atoms. In the fifth Sn site, Sn is bonded in a 12-coordinate geometry to three Y and six Fe atoms. In the sixth Sn site, Sn is bonded in a 6-coordinate geometry to six Fe atoms. In the seventh Sn site, Sn is bonded in a 7-coordinate geometry to one Y and six Fe atoms. In the eighth Sn site, Sn is bonded in a 8-coordinate geometry to one Y, six Fe, and one Sn atom. The Sn–Sn bond length is 2.94 Å. In the ninth Sn site, Sn is bonded in a 8-coordinate geometry to one Y, six Fe, and one Sn atom. The Sn–Y bond length is 3.02 Å. All Sn–Fe bond lengths are 2.83 Å. The Sn–Sn bond length is 2.95 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Electronic and magnetic properties of hole-doped topological kagome Fe 1−𝑥 ⁢Mn 𝑥 ⁢Sn thin films

We have investigated the electronic and magnetic structures of topological kagome Fe 1−𝑥 ⁢Mn 𝑥 ⁢Sn (0 ≤ 𝑥 ≤ 0.3) thin films via neutron diffraction, electronic transport measurements, and ab initio density functional theory (DFT) to understand the interplay between hole doping, magnetism, and the electronic structures. Temperature-dependent neutron diffraction measurements on parent FeSn reveal the Néel temperature to be 𝑇 N ∼ 355 K and the underlying A-type antiferromagnetic ordering is associated with a wave vector 𝒒 = (001/2). Upon Mn doping to 𝑥 = 0.15, 𝑇 N decreases slightly while the magnetic ordering vector remains the same. Resistivity measurements show metallic characteristics and in-plane anisotropy down to 10 K for all the investigated samples. The effects of hole doping are mapped in terms of electronic ground state calculations via DFT which show that the Dirac point is moved closer to the Fermi level (𝐸 F ) and the flat bands get pushed away from 𝐸 F upon hole doping. However, a comparison between hole-doped Fe 1−𝑥⁢ Mn 𝑥⁢ Sn and electron-doped Fe 1−𝑥 ⁢Co 𝑥 ⁢Sn indicates that the Néel temperature does not scale with the position of 𝐸 F relative to the flat band. Furthermore, our results establish the antiferromagnetic state of FeSn and Fe 1−𝑥 ⁢Mn 𝑥⁢ Sn films at room temperature, laying the groundwork for future studies of magnetism in kagome heterostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Simultaneous Development of Antiferromagnetism and Local Symmetry Breaking in a Kagome Magnet (Co 0.45 Fe 0.55 )Sn

CoSn and FeSn, two kagome-lattice metals, have recently attracted significant attention as hosts of electronic flat bands and emergent physical properties. However, current understandings of their physical properties are limited to knowledge of the average crystal structure. Here, we report the Fe-doping induced coemergence of the antiferromagentic (AFM) order and local symmetry breaking in (Co 0.45 Fe 0.55 )Sn. Rietveld analysis on the neutron and synchrotron X-ray diffraction data indicates A-type antiferromagnetic order with the moment pointing perpendicular to the kagome layers, associated with the anomaly in the MSn(1) 2 Sn(2) 4 (M = Co/Fe) octahedral distortion and the lattice constant c. Reverse Monte Carlo (RMC) modeling of the synchrotron X-ray total scattering results captured the subtle local orthorhombic distortion involving off-axis displacements of Sn(2). Our results indicate that the stable hexagonal lattice above T N becomes unstable once the A-type AFM order is formed below T N . Here we argue that the local symmetry breaking has a magnetic origin, since the spatially varied M–Sn(2) bond lengths arise from out-of-plane magnetic exchange coupling J c via the exchange pathway M–Sn(2)–M. Our study provides comprehensive information on the crystal structure in both long-range scale and local scale, unveiling unique coupling between AFM order, octahedral distortion, and hidden local symmetry breaking.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Persistent flat band splitting and strong selective band renormalization in a kagome magnet thin film

Magnetic kagome materials provide a fascinating playground for exploring the interplay of magnetism, correlation and topology. Many magnetic kagome systems have been reported including the binary Fe m X n (X = Sn, Ge; m:n = 3:1, 3:2, 1:1) family and the rare earth RMn 6 Sn 6 (R = rare earth) family, where their kagome flat bands are calculated to be near the Fermi level in the para magnetic phase. While partially filling a kagome flat band is predicted to give rise to a Stoner-type ferromagnetism, experimental visualization of the mag netic splitting across the ordering temperature has not been reported for any of these systems due to the high ordering temperatures, hence leaving the nature of magnetism in kagome magnets an open question. Here, we probe the electronic structure with angle-resolved photoemission spectroscopy in a kagome magnet thin film FeSn synthesized using molecular beam epitaxy. We identify the exchange-split kagome flat bands, whose splitting persists above the magnetic ordering temperature, indicative of a local moment picture. Such local moments in the presence of the topological flat band are consistent with the compact molecular orbitals predicted in theory. We further observe a large spin-orbital selective band renormalization in the Fe d xy + d x 2 -y 2 spin majority channel reminiscent of the orbital selective correlation effects in the iron based superconductors. Our discovery of the coexistence of local moments with topological flat bands in a kagome system echoes similar findings in magic-angle twisted bilayer graphene, and provides a basis for theoretical effort towards modeling correlation effects in magnetic flat band systems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Carrier- and strain-tunable intrinsic magnetism in two-dimensional $MAX_3$ transition metal chalcogenides

Here, we present a density functional theory study of the carrier-density and strain dependence of magnetic order in two-dimensional (2D) $MAX_3$ ($\textit{M}$ = V, Cr, Mn, Fe, Co, Ni; $\textit{A}$ = Si, Ge, Sn; and $\textit{X}$ = S, Se, Te) transition metal trichalcogenides. Our ab initio calculations show that this class of compounds includes wide and narrow gap semiconductors, metals, and half-metals, and that most of these compounds are magnetic. Although antiferromagnetic order is most common, ferromagnetism is predicted in $\textit{M}$SiSe 3 for $\textit{M}$ = Mn and Ni; in $\textit{M}$SiTe 3 for $\textit{M}$ = V and Ni; in MnGeSe 3 ; $\textit{M}$GeTe 3 for $\textit{M}$ = Cr, Mn, and Ni; in FeSnS 3 ; and in MSnTe 3 for $\textit{M}$ = V, Mn, and Fe. Among these compounds CrGeTe 3 , VSnTe 3 , and CrSnTe 3 are ferromagnetic semiconductors. Our calculations suggest that the competition between antiferromagnetic and ferromagnetic order can be substantially altered by strain engineering, and in the semiconductor case also by gating. The associated critical temperatures can be enhanced by means of carrier doping and strains.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Flat bands in the CoSn-type compounds

Quantum interference on the kagome lattice generates electronic bands with narrow bandwidth, called flat bands. Crystal structures incorporating this lattice can host strong electron correlations with nonstandard ingredients, but only if these bands lie at the Fermi level. In the six compounds with the CoSn structure type (FeGe, FeSn, CoSn, NiIn, RhPb, and PtTl) the transition metals form a kagome lattice. The two iron variants are robust antiferromagnets so we focus on the latter four and investigate their thermodynamic and transport properties. We consider these results and calculated band structures to locate and characterize the flat bands in these materials. Finally, we propose that CoSn and RhPb deserve the community's attention for exploring flat-band physics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

How correlations change the magnetic structure factor of the kagome Hubbard model

The kagome Hubbard model (KHM) is a paradigmatic example of a frustrated two-dimensional model. While its strongly correlated regime, described by a Heisenberg model, is of topical interest due to its enigmatic prospective spin-liquid ground state, the weakly and moderately correlated regimes remain largely unexplored. Motivated by the rapidly growing number of metallic kagome materials (e.g., Mn 3 Sn, Fe 3 Sn 2 , FeSn, Co 3 Sn 2 S 2 , Gd 3 Ru 4 Al 12 , and AV 3 Sb 5 with A = K, Rb, Cs), here we study the respective regimes of the KHM by means of three complementary numerical methods: the dynamical mean-field theory, the dynamical vertex approximation, and determinant quantum Monte Carlo. In contrast to the archetypal square lattice, we find no tendencies toward magnetic ordering, as magnetic correlations remain short-range. Nevertheless, the magnetic correlations undergo a remarkable crossover as the system approaches the metal-to-insulator transition. The Mott transition itself does not affect the magnetic correlations. Our equal-time and dynamical structure factors can be used as a reference for inelastic neutron scattering experiments on the growing family of metallic kagome materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Understanding magnetic phase coexistence in Ru 2 Mn 1-x Fe x Sn Heusler alloys: A neutron scattering, thermodynamic, and phenomenological analysis

The random substitutional solid solution between the antiferromagnetic (AFM) full-Heusler alloy Ru 2 MnSn and the ferromagnetic (FM) full-Heusler alloy Ru 2 FeSn provides a rare opportunity to study FM-AFM phase competition in a near-lattice-matched, cubic system, with full solubility. At intermediate x in Ru 2 Mn 1-x Fe x Sn this system displays suppressed magnetic ordering temperatures, spatially coexisting FM and AFM order, and strong coercivity enhancement, despite rigorous chemical homogeneity. Here, we construct the most detailed temperature- and x-dependent understanding of the magnetic phase competition and coexistence in this system to date, combining wide-temperature-range neutron diffraction and small-angle neutron scattering with magnetometry and specific heat measurements on thoroughly characterized polycrystals. A complete magnetic phase diagram is generated, showing FM-AFM coexistence between x ≈ 0.30 and x ≈ 0.70. Furthermore, important insight is gained from the extracted length scales for magnetic phase coexistence (25–100 nm), the relative magnetic volume fractions and ordering temperatures, and remarkable x-dependent trends in magnetic and electronic contributions to specific heat. An unusual feature in the magnetic phase diagram (an intermediate FM phase) is also shown to arise from an extrinsic effect related to a minor Ru-rich secondary phase. The established magnetic phase diagram is then discussed with the aid of phenomenological modeling, clarifying the nature of the mesoscale phase coexistence with respect to the understanding of disordered Heisenberg models.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Deciphering and Manipulating Low Dimensional Magnetism

This program investigates the electronic structure and collective quantum phenomena of correlated magnetic materials using advanced angle-resolved photoemission spectroscopy (ARPES) and complementary probes, with a focus on three interrelated material families: (i) the semiconducting van der Waals magnet Cr₂Ge₂Te₆, (ii) metallic Fe-based van der Waals magnets including Fe₃GeTe₂ Fe₃GaTe₂, and Fe5GeTe₂, and (iii) kagome magnets such as FeGe, FeSn, and CsV₃Sb₅/CsCr₃Sb₅. In Cr₂Ge₂Te₆, our work established how spin excitations develop across a dimensional crossover as spins establish correlation to form long range order, providing a clean platform to isolate correlation effects. In metallic Fe-based magnets, we uncovered the dichotomy between flat and dispersive bands, revealed momentum-dependent electronic reconstructions tied to magnetic order, and demonstrated reversible, non-volatile electronic switching near room temperature, highlighting the strong coupling among spin, charge, and lattice degrees of freedom in metallic ferromagnets. In kagome magnets, we identified charge density wave formation, symmetry breaking, flat-band renormalization, and field-induced momentum-dependent electronic anisotropy, elucidating how geometric frustration and electronic correlations conspire to generate emergent quantum states. Collectively, these results establish a unified microscopic framework for understanding correlation-driven electronic reconstruction, symmetry breaking, and collective order across semiconducting and metallic magnetic systems, advancing DOE mission goals in quantum materials discovery and control.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗