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Shirako Y.,Gakushuin University | Shirako Y.,Superconducting Properties Unit | Shirako Y.,Nagoya University | Wang X.,Superconducting Properties Unit | And 16 more authors.
Inorganic Chemistry | Year: 2014

The polycrystalline MO2's (HP-PdF2-type MO2, M = Rh, Os, Pt) with high-pressure PdF2 compounds were successfully synthesized under high-pressure conditions for the first time, to the best of our knowledge. The crystal structures and electromagnetic properties were studied. Previously unreported electronic properties of the polycrystalline HP-PdF2-type RuO2 and IrO2 were also studied. The refined structures clearly indicated that all compounds crystallized into the HP-PdF2-type structure, M4+O2- 2, rather than the pyrite-type structure, Mn+(O2)n (n < 4). The MO2 compounds (M = Ru, Rh, Os, Ir) exhibited metallic conduction, while PtO2 was highly insulating, probably because of the fully occupied t2g band. Neither superconductivity nor a magnetic transition was detected down to a temperature of 2 K, unlike the case of 3d transition metal chalcogenide pyrites. © 2014 American Chemical Society.

Sun Y.,Beihang University | Wang C.,Beihang University | Huang Q.,U.S. National Institute of Standards and Technology | Guo Y.,Superconducting Properties Unit | And 3 more authors.
Inorganic Chemistry | Year: 2012

The antiperovskite Mn 3ZnN is studied by neutron diffraction at temperatures between 50 and 295 K. Mn 3ZnN crystallizes to form a cubic structure at room temperature (C1 phase). Upon cooling, another cubic structure (C2 phase) appears at around 177 K. Interestingly, the C2 phase disappears below 140 K. The maximum mass concentration of the C2 phase is approximately 85% (at 160 K). The coexistence of C1 and C2 phase in the temperature interval of 140-177 K implies that phase separation occurs. Although the C1 and C2 phases share their composition and lattice symmetry, the C2 phase has a slightly larger lattice parameter (Δa ≈ 0.53%) and a different magnetic structure. The C2 phase is further investigated by neutron diffraction under high-pressure conditions (up to 270 MPa). The results show that the unusual appearance and disappearance of the C2 phase is accompanied by magnetic ordering. Mn 3ZnN is thus a valuable subject for study of the magneto-lattice effect and phase separation behavior because this is rarely observed in nonoxide materials. © 2012 American Chemical Society.

Wang X.,Superconducting Properties Unit | Wang X.,Hokkaido University | Guo Y.,Superconducting Properties Unit | Guo Y.,University of Oxford | And 6 more authors.
Journal of Solid State Chemistry | Year: 2013

The effects of substituting Co on the spin-chain compound Sr 3Co2O6 with Zn were investigated by synchrotron X-ray diffraction, magnetic susceptibility, isothermal magnetization, and specific heat measurements. To the best of our knowledge, this is the first report to describe the successful substitution of Co in Sr3Co 2O6 with Zn. The substitution was carried out by a method involving high pressures and temperatures to obtain Sr3CoZnO 6, which crystalized into a K4CdCl6-derived rhombo-hedral structure with a space group of R-3c, similar to the host compound. With the Zn substitution, the Ising-type magnetic anisotropy of the host compound remarkably reduced; the newly formed Sr3CoZnO 6 became magnetically isotropic with Heisenberg-type characteristics. This could probably be ascribed to the establishment of a different interaction pathway, -Co4+(S = 1/2)-O-Zn2+(S=0)-O-Co4+(S = 1/2)-. Details of the magnetic properties of Zn substituted Sr 3Co2O6 were reported. © 2013 Elsevier Inc.

News Article | January 14, 2016
Site: phys.org

Figure: (a) Schematic of an osmium oxide (NaOsO3) crystal structure and (b) an optical microscope image of the single crystal. Credit: National Institute for Materials Science A research team led by Kazunari Yamaura, chief researcher, Superconducting Properties Unit, National Institute for Materials Science (NIMS), Japan, and Dr. Stuart Calder and others at the Oak Ridge National Laboratory in the United States, jointly demonstrated that the strongest ever spin-phonon coupling was observed in osmium oxide synthesized for the first time in the world by NIMS in 2009. A general belief is that the stronger the coupling between various properties in a material is, the more advantageous it is in the development of a new functional material. As such, the osmium oxide may serve as a candidate for a next-generation functional material useful in the areas of information & technology and electronics. While platinum group elements and their compounds are widely used as catalysts, their other functions have not been explored very much, partly because they are expensive. Amid the situation, the NIMS research team discovered that the osmium oxide it synthesized in 2009 exhibits an unusual magnetic transition at about 140°C, which is higher than room temperature, and had been taking on the challenge of pioneering non-catalytic, industrial functions of the material. Based on the recent observation of spin-phonon coupling in the osmium oxide, the team found that the coupling was the strongest ever observed. The strong spin-phonon coupling may be caused by the outermost orbitals of osmium atoms as they are greatly extended outward in space, in the solid oxide. The fact that this structural characteristic is common to all platinum group elements suggests that compounds based on these elements other than osmium are also likely to be associated with strong spin-phonon coupling. Spin-phonon coupling directly represents the strength of interaction between magnetism (spin) and the crystal lattice system (phonon). Recent studies indicate that the stronger the spin-phonon interaction is, the more favorable it is in the development of new materials—such as a multiferroic material, for example—in which the coupling of magnetism and the lattice system has great importance. Expectations are rising for the multiferroic material as a candidate for an innovative functional material, as it may contribute to the realization of power-saving high-density information-recording elements and power-saving ultra-high-speed logic elements. This study is considered to be a major step toward this endeavor. This research was carried out in the framework of the NIMS 3rd Mid-Term Program project on advanced superconducting materials. Explore further: Development of 'Slater insulator' that rapidly changes from conductor to insulator at room temperature More information: S. Calder et al. Enhanced spin-phonon-electronic coupling in a 5d oxide, Nature Communications (2015). DOI: 10.1038/ncomms9916

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