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The compound Ba 2 ZnSb 2 has been predicted to be a promising thermoelectric material, potentially achieving zT > 2 at 900 K due to its one-dimensional chains of edge-shared [ZnSb 4/2 ] 4- tetrahedra and interspersed Ba cations. However, the high air sensitivity of this material makes it difficult to measure its thermoelectric properties. In this work, isovalent substitution of Eu for Ba was carried out to make Ba 2- x Eu x ZnSb 2 in order to improve the stability of the material in air and to allow characterization of thermal and electronic properties of three different compositions ( x = 0.2, 0.3, and 0.4). Polycrystalline samples were synthesized using binary precursors via ball milling and annealing, and their thermoelectric properties were measured. Samples showed low thermal conductivity (<0.8 W/m K), a high Seebeck coefficient (350-550 μV/K), and high charge carrier mobility (20-35 cm 2 /V) from 300 to 500 K, consistent with predictions of high thermoelectric efficiency. Evaluation of the thermoelectric quality factor suggests that a higher zT can be attained if the carrier concentration can be increased via doping.

The structure, magnetic properties, and 151 Eu and 119 Sn Mössbauer spectra of the solid-solution Eu 11- x Sr x Zn 4 Sn 2 As 12 are presented. A new commensurately modulated structure is described for Eu 11 Zn 4 Sn 2 As 12 ( R 3 m space group, average structure) that closely resembles the original structural description in the monoclinic C 2/ c space group with layers of Eu, puckered hexagonal Zn 2 As 3 sheets, and Zn 2 As 6 ethane-like isolated pillars. The solid-solution Eu 11- x Sr x Zn 4 Sn 2 As 12 (0 < x < 10) is found to crystallize in the commensurately modulated R 3 space group, related to the parent phase but lacking the mirror symmetry. Eu 11 Zn 4 Sn 2 As 12 orders with a saturation plateau at 1 T for 7 of the 11 Eu 2+ cations ferromagnetically coupled (5 K) and shows colossal magnetoresistance at 15 K. The magnetic properties of Eu 11 Zn 4 Sn 2 As 12 are investigated at higher fields, and the ferromagnetic saturation of all 11 Eu 2+ cations occurs at ∼8 T. The temperature-dependent magnetic properties of the solid solution were investigated, and a nontrivial structure-magnetization correlation is revealed. The temperature-dependent 151 Eu and 119 Sn Mössbauer spectra confirm that the europium atoms in the structure are all Eu 2+ and that the tin is consistent with an oxidation state of less than four in the intermetallic region. The spectral areas of both Eu(II) and Sn increase at the magnetic transition, indicating a magnetoelastic effect upon magnetic ordering.

A method is presented for synthesizing core-shell nanoparticles with a magnetic core and a porous shell suitable for drug delivery and other medical applications. The core contains multiple $\gamma$-Fe$&#95;2$O$&#95;3$ nanoparticles ($\sim$15~nm) enclosed in a SiO$&#95;2$ ($\sim$100-200~nm) matrix using either methyl (denoted TMOS-$\gamma$-Fe$&#95;2$O$&#95;3$) or ethyl (TEOS-$\gamma$-Fe$&#95;2$O$&#95;3$) template groups. Low-temperature M{\"o}ssbauer spectroscopy showed that the magnetic nanoparticles have the maghemite structure, $\gamma$-Fe$&#95;2$O$&#95;3$, with all the vacancies in the octahedral sites. Saturation magnetization measurements revealed that the density of $\gamma$-Fe$&#95;2$O$&#95;3$ was greater in the TMOS-$\gamma$-Fe$&#95;2$O$&#95;3$ nanoparticles than TEOS-$\gamma$-Fe$&#95;2$O$&#95;3$ nanoparticles, presumably because of the smaller methyl group. Magnetization measurements showed that the blocking temperature is around room temperature for the TMOS-$\gamma$-Fe$&#95;2$O$&#95;3$ and around 250~K for the TEOS-$\gamma$-Fe$&#95;2$O$&#95;3$. Three dimensional topography analysis shows clearly that the magnetic nanoparticles are not only at the surface but have penetrated deep in the silica to form the core-shell structure., (© 2020 IOP Publishing Ltd.)

Solid-state ionic approaches for modifying ion distributions in getter/oxide heterostructures offer exciting potentials to control material properties. Here, we report a simple, scalable approach allowing for manipulation of the superconducting transition in optimally doped YBa 2 Cu 3 O 7-δ (YBCO) films via a chemically driven ionic migration mechanism. Using a thin Gd capping layer of up to 20 nm deposited onto 100 nm thick epitaxial YBCO films, oxygen is found to leach from deep within the YBCO. Progressive reduction of the superconducting transition is observed, with complete suppression possible for a sufficiently thick Gd layer. These effects arise from the combined impact of redox-driven electron doping and modification of the YBCO microstructure due to oxygen migration and depletion. This work demonstrates an effective step toward total ionic tuning of superconductivity in oxides, an interface-induced effect that goes well into the quasi-bulk regime, opening-up possibilities for electric field manipulation.

Experimental and theoretical investigations on itinerant ferromagnetic systems under pressure have shown that ferromagnetic quantum criticality is avoided either by a change of the transition order, becoming of the first order at a tricritical point, or by the appearance of modulated magnetic phases. In the first case, the application of a magnetic field reveals a wing-structure phase diagram as seen in itinerant ferromagnets such as ZrZn 2 and UGe 2 . In the second case, no tricritical wings have been observed so far. Here, we report on the discovery of wing-structure as well as the appearance of modulated magnetic phases in the temperature-pressure-magnetic field phase diagram of LaCrGe 3 . Our investigation of LaCrGe 3 reveals a double-wing structure indicating strong similarities with ZrZn 2 and UGe 2 . But, unlike these simpler systems, LaCrGe 3 also shows modulated magnetic phases similar to CeRuPO. This finding provides an example of an additional possibility for the phase diagram of metallic quantum ferromagnets.The study of phase transitions in quantum ferromagnets has shown that the approach to a continuous quantum ferromagnetic transition is typically interrupted by either a tricritical point or a new magnetic phase. Here the authors show that LaCrGe 3 exhibits both these features in its phase diagram.

Planar hydrocarbon-like metal clusters may foster new insights linking organic molecules with conjugated π-π bonding interactions and inorganic structures in terms of their bonding characteristics. However, such clusters are uncommon in polar intermetallics. Herein, we report two polar intermetallic phases, Pr 5 Co 2 Ge 3 and Pr 7 Co 2 Ge 4 , both of which feature such planar metal clusters, namely, ethylene-like [Co 2 Ge 4 ] clusters plus the concatenated forms and polyacene-like [Co 2 Ge 2 ] n ribbons in Pr 5 Co 2 Ge 3 , and 1,2,4,5-tetramethylbenzene-like [Co 4 Ge 6 ] cluster in Pr 7 Co 2 Ge 4 . Just as in the related planar organic structures, these metal-metalloid species are dominated by covalent bonding interactions. Both compounds magnetically order at low temperature with net ferromagnetic components: Pr 5 Co 2 Ge 3 through a series of transitions below 150 K and Pr 7 Co 2 Ge 4 through a single ferromagnetic transition at 19 K. Spin-polarized electronic structure calculations for Pr 7 Co 2 Ge 4 reveal strong spin-orbit coupling within Pr and considerable magnetic contributions from Co atoms. This work suggests that similar structural chemistry can emerge for other rare-earth/late-transition-metal/main-group systems., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)