Browsing by Author "Nakano, K"

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    Superconductivity in BaTi2Sb2O with a d1 square lattice
    (Physical Society of Japan, 2012-10-01) Yajima, T; Nakano, K; Takeiri, F; Ono, T; Hosokoshi, Y; Matsushita, Y; Hester, JR; Kobayashi, Y; Kageyama, H
    We prepared a new two-dimensional oxyantimonide, BaTi(2)Sb(2)O, which shows a superconducting transition at 1.2 K, representing the first superconductivity in a system with Ti(3+) (d(1)) in a square lattice. The TiO(2)Sb(4) mixed anionic coordination stabilizes a unique half-filled Ti d(xy) orbital configuration in Ti(2)O plane, which is analogous to Cu(2+) (d(9)) in the high-T(c) superconductors. A charge density wave (CDW)- or spin density wave (SDW)-like anomaly appears at 50 K, which is significantly reduced compared with 200 K for the isostructural and non-superconducting BaTi(2)As(2)O. © 2012, Physical Society of Japan
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    Synthesis and physical properties of the new oxybismuthides BaTi2Bi2O and (SrF)2Ti2Bi2O with a d1 square net
    (Physical Society of Japan, 2012-12-11) Yajima, T; Nakano, K; Takeiri, F; Hester, JR; Yamamoto, T; Kobayashi, Y; Tsuji, N; Kim, J; Fujiwara, A; Kageyama, H
    We have recently reported the d(1) square-lattice compound BaTi(2)Sb(2)O, which shows superconductivity at T(c) = 1.2K coexisting with a charge- or spin-density wave (CDW/SDW) state. Here, we successfully prepared two new oxybismuthides, BaTi(2)Bi(2)O and (SrF)(2)Ti(2)Bi(2)O, as the first Pn = Bi compounds in the ATi(2)Pn(2)O family. The CDW/SDW state disappeared for both compounds, presumably owing to the considerable interaction between the Ti-3d and Bi-6s orbitals. The complete suppression of the CDW/SDW instability resulted in an enhanced T(c) of 4.6 K for BaTi(2)Bi(2)O. However, (SrF)(2)Ti(2)Bi(2)O exhibits no superconductivity, suggesting the importance of the interlayer interaction for superconductivity. © 2012, Physical Society of Japan
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    T-c enhancement by aliovalent anionic substitution in superconducting BaTi2(Sb1-xSnx)2O
    (Physical Society Japan, 2013-07-01) Nakano, K; Yajima, T; Takeiri, F; Green, MA; Hester, JR; Kobayashi, Y; Kageyama, H
    BaTi2Sb2O is a T-c = 1.2 K superconductor with a d(1) square lattice, and isovalent Bi substitution for Sb can increase its T-c to 4.6 K (BaTi2Bi2O), accompanied by the complete suppression of charge density wave (CDW) or spin density wave (SDW) transition. In the present study, we demonstrate that aliovalent Sn substitution (hole doping) also increases T-c up to 2.5 K for BaTi2(Sb0.7Sn0.3)(2)O, while suppressing CDW/SDW transition only slightly. The overall electronic phase diagram of BaTi2(Sb, Sn)(2)O is qualitatively similar to that of cation-substituted (hole-doped) (Ba,Na)Ti2Sb2O, but quantitative differences such as in T-c are observed, which is discussed in terms of Ti-Pn hybridization and chemical disorder. © 2013, Physical Society of Japan