We report the synthesis, crystal structure, and basic properties of the new intermetallic compound Sc3Mn3Al7Si5. The structure of the compound was established by single-crystal X-ray diffraction, and ...it crystallizes with a hexagonal structure (Sc3Ni11Si4 type) with Mn atoms forming the Kagome nets. The dc magnetic susceptibility measurements reveal a Curie–Weiss moment of ∼0.51 μB/Mn; however, no magnetic order is found for temperatures as low as 1.8 K. Electrical resistivity and heat capacity measurements show that this compound is definitively metallic, with a relatively large specific heat Sommerfeld coefficient, indicating strong electronic correlations. Intriguingly, these features have revealed Sc3Mn3Al7Si5 as a possible quantum spin liquid. With chemical and lattice disorder introduced by doping, a spin liquid to spin glass transition is observed in the highest Ga-doped compounds. The roles of the geometrically frustrated structure and Mn-ligand hybridization in the magnetism of the title compounds are also discussed.
We synthesized monodisperse nanospheres of an intermetallic FeSn5 phase via a nanocrystal-conversion protocol using preformed Sn nanospheres as templates. This tetragonal phase in P4/mcc space group, ...along with the defect structure Fe0.74Sn5 of our nanospheres, has been resolved by synchrotron X-ray diffraction and Rietveld refinement. Importantly, FeSn5, which is not yet established in the Fe–Sn phase diagram, exhibits a quasi-one dimensional crystal structure along the c-axis, thus leading to interesting anisotropic thermal expansion and magnetic properties. Magnetization measurements indicate that nanospheres are superparamagnetic above the blocking temperature T B = 300 K, which is associated with the higher magnetocrystalline anisotropy constant K = 3.33 kJ m–3. The combination of the magnetization measurements and first-principles density functional theory calculations reveals the canted antiferromagnetic nature with significant spin fluctuation in lattice a–b plane. The low Fe concentration also leads Fe0.74Sn5 to enhanced capacity as an anode in Li ion batteries.
The lack of a mechanistic framework for chemical reactions forming inorganic extended solids presents a challenge to accelerated materials discovery. We demonstrate here a combined computational and ...experimental methodology to tackle this problem, in which in situ X-ray diffraction measurements monitor solid-state reactions and deduce reaction pathways, while theoretical computations rationalize reaction energetics. The method has been applied to the La
CuO
S
(0 ≤
≤ 4) quaternary system, following an earlier prediction that enhanced superconductivity could be found in these new lanthanum copper(II) oxysulfide compounds. In situ diffraction measurements show that reactants containing Cu(II) and S(2-) ions undergo redox reactions, leaving their ions in oxidation states that are incompatible with forming the desired new compounds. Computations of the reaction energies confirm that the observed synthetic pathways are indeed favored over those that would hypothetically form the suggested compounds. The consistency between computation and experiment in the La
CuO
S
system suggests a role for predictive theory: to identify and to explicate new synthetic routes for forming predicted compounds.
Broadband tunability is a central theme in contemporary nanophotonics and metamaterials research. Combining metamaterials with phase change media offers a promising approach to achieve such ...tunability, which requires a comprehensive investigation of the electromagnetic responses of novel materials at subwavelength scales. In this work, we demonstrate an innovative way to tailor band-selective electromagnetic responses at the surface of a heavy fermion compound, samarium sulfide (SmS). By utilizing the intrinsic, pressure sensitive, and multi-band electron responses of SmS, we create a proof-of-principle heavy fermion metamaterial, which is fabricated and characterized using scanning near-field microscopes with <50 nm spatial resolution. The optical responses at the infrared and visible frequency ranges can be selectively and separately tuned via modifying the occupation of the 4f and 5d band electrons. The unique pressure, doping, and temperature tunability demonstrated represents a paradigm shift for nanoscale metamaterial and metasurface design.
The reproducible gram-scale synthesis of crystalline nanoscale multiferroics is critical for the development of the next generation of commercially relevant electronic devices. Of the subset of ...multiferroic materials, yttrium manganese oxide (YMnO3) is highly attractive, because of its large magneto-electric coupling constants and the recent observation of giant polarization under pressure in these types of rare earth manganites. Utilizing a unique synthetic methodology that combines metal–oleate thermal degradation with the use of a molten salt protocol, we were able to reproducibly generate monodisperse distributions of morphologically distinctive yttrium manganese oxides. Specifically, using a molten NaCl flux, we were able to synthesize phase-pure, single-crystalline hexagonal YMnO3 nanoplates, measuring 441 ± 241 nm in diameter and 46 ± 6 nm in height. Moreover, these nanoplates gave rise to multiferroic behavior, which was confirmed by the observation of a ferroelectric phase from a combination of high-resolution TEM (HRTEM) and selected-area electron diffraction (SAED) analysis. Magnetic measurements are consistent with the onset of a spin glass state below 5 K. To highlight the generalizability of the synthetic method we have developed herein, as a demonstration of principle, we have also successfully used the same protocol to produce nanocubes of lanthanum aluminum oxide (LaAlO3).
We report a large linear magnetoresistance in Cu2−xTe, reaching Δρ/ρ(0) = 250% at 2 K in a 9 T field, for samples with x = 0.13 to 0.22. These results are comparable to those for Ag2X materials, ...though for Cu2−xTe the carrier densities are considerably larger. Examining the magnitudes and the crossover from quadratic to high-field linear behavior, we show that models based on classical transport behavior best explain the observed results. The effects are traced to the misdirection of currents in high mobility transport channels, likely due to behavior at grain boundaries such as topological surface states or a high mobility interface phase. The resistivity also exhibits a T2 dependence in the temperature range where the large linear MR appears, an indicator of electron-electron interaction effects within the high mobility states. Thus this is an example of a system in which electron-electron interactions dominate the low-temperature linear magnetoresistance.
The lack of a mechanistic framework for chemical reactions forming inorganic extended solids presents a challenge to accelerated materials discovery. We demonstrate here a combined computational and ...experimental methodology to tackle this problem, in which in situ X-ray diffraction measurements monitor solid-state reactions and deduce reaction pathways, while theoretical computations rationalize reaction energetics. The method has been applied to the La₂CuO4–xSₓ (0 ≤ x ≤ 4) quaternary system, following an earlier prediction that enhanced superconductivity could be found in these new lanthanum copper(II) oxysulfide compounds. In situ diffraction measurements show that reactants containing Cu(II) and S(2−) ions undergo redox reactions, leaving their ions in oxidation states that are incompatible with forming the desired new compounds. Computations of the reaction energies confirm that the observed synthetic pathways are indeed favored over those that would hypothetically form the suggested compounds. The consistency between computation and experiment in the La₂CuO4–xSₓ system suggests a role for predictive theory: to identify and to explicate new synthetic routes for forming predicted compounds.
The ternary compound “YbPtIn2” has been synthesized and its crystal structure determined using single crystal X-ray diffraction techniques. The compound crystallizes in the MgCuAl2 structure, a ...ternary structure type often formed when rare earth metals, Group 10 transition metals, and indium are present in a 1:1:2 ratio. The unit cell is C-centered orthorhombic, space group Cmcm (#63) with lattice parameters of a=4.3410(1)Å, b=10.3230(2)Å, and c=7.8510(2)Å. Evidence is found for a substantial non-stoichiometry on the Yb site, in contrast to the Pt and In sites which behave as expected, and it is believed that the stoichiometry of this compound is more properly described as Yb0.95PtIn2. Magnetic and resistivity measurements reveal that “YbPtIn2” is a weakly interacting, non-magnetic metal exclusively containing Yb2+, and with a resistivity (ρ) varying from 34μΩcm at room temperature to a residual resistivity ρ0 of 23μΩcm at 1.8K. Density functional theory calculations suggest that the observed diamagnetic Yb behavior is expected for this compound, but that certain substitutions on the Pt or In site could help stabilize magnetic Yb3+ and potentially induce heavy fermion behavior.
The crystal structure, magnetic behavior, and temperature-dependent resistivity of the new ternary compound Yb0.95PtIn2. Display omitted
► Flux growth method used to produce Yb0.95PtIn2 single crystals. ► Found rare example of non-stoichiometry in a MgCuAl2-type structure. ► The resistivity and diamagnetic response of Yb0.95PtIn2 were modeled. ► DFT correctly predicts presence of Yb2+ in Yb0.95PtIn2. ► COHP results suggest other MgCuAl2-type indides that may contain paramagnetic Yb3+.
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