Browsing by Author "Kakurai, K"

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    A quantum multi-critical point in CeCu6−xAux
    (Elsevier B. V., 2006-11-15) Robinson, RA; Goossens, DJ; Torikachvili, MS; Kakurai, K; Okumura, H
    CeCu6−xAux is a well-known heavy-fermion system in which the ground state is antiferromagnetically ordered for x>0.1 and temperatures below 1 K. Non-Fermi liquid behaviour occurs around this critical concentration. The parent compound, CeCu6, exhibits a structural phase transition near 230 K, where it changes from the Pnma orthorhombic room-temperature structure to the P21/c monoclinic structure. The monoclinicity increases as temperature falls, with β reaching 91.44° at 10 K. In the work presented here, powder neutron diffraction is used to explore the monoclinicity at 8 K as a function of composition for 0.00.1, indicates that long-range order disappears at exactly the same critical concentration. At a minimum, the structural distortion and antiferromagnetism seem to be competing with each other, and this raises the intriguing possibility that lattice degrees of freedom are important in the non-Fermi liquid regime.
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    Stabilization of spin and charge ordering in stoichiometric YbFe2O4
    (Physical Society of Japan, 2019-03-15) Fujiwara, K; Karasudani, T; Kakurai, K; Lee, WT; Rule, KC; Studer, AJ; Ikeda, N
    We report a wide-range reciprocal space observation with neutron diffraction in an iron vacancy controlled YbFe2O4 crystal, which is proposed as a prototype of electronic ferroelectrics arising from iron charge ordering. The increase of the charge ordering transition temperature and the disappearance of spin competitive transition were discovered in this stoichiometric crystal. We suppose that the lower ionic deficiency of this crystal enhances the development of spin and charge order coherence length, and consequently, the intrinsic nature of spin and charge ordering of YbFe2O4 could be detected. The experiment was performed with a two-dimensional neutron detector, and all super-lattice spots and its modulations above magnetic ordering temperature TN = 245 K are successfully explained with six domains of a monoclinic charge-order super-lattice cell. A rather extended two dimensional (2D) spin correlation above TN was identified with polarized 3He neutron spin filter and we found a clear indication of a coupling between the 2D spin correlation and charge ordering between TN and 300 K, at which a new lattice distortion phase may set in. ©2019 The Physical Society of Japan.