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Robust atomic orbital in the cluster magnet LiMoO2

N. Katayama, H. Takeda, T. Yamaguchi, Y. Yamada, K. Iida, M. Takigawa, Y. Ohta, and H. Sawa
Phys. Rev. B 102, 081106(R) – Published 7 August 2020
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    Abstract

    In this study, we present a rutile-related material, LiMoO2, that becomes a cluster magnet and exhibits a spin singlet formation on a preformed molybdenum dimer upon cooling. Unlike ordinary cluster magnets, the atomic dyz orbital robustly survives despite the formation of molecular orbitals, thereby affecting the magnetic properties of the selected material. Such hybrid cluster magnets with the characters of molecular and atomic orbitals realize multiple independent spins on an isolated cluster, leading to an ideal platform to study the isolated spin dimers physics.

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    • Received 2 March 2020
    • Revised 6 June 2020
    • Accepted 28 July 2020

    DOI:https://doi.org/10.1103/PhysRevB.102.081106

    ©2020 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Chemical bondingElectronic structureMagnetic orderMagnetic susceptibility
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    N. Katayama1,*, H. Takeda2, T. Yamaguchi3, Y. Yamada1, K. Iida4, M. Takigawa2, Y. Ohta3, and H. Sawa1

    • 1Department of Applied Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
    • 2Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
    • 3Department of Physics, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
    • 4Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan

    • *katayama.naoyuki@b.mbox.nagoya-u.ac.jp

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    Vol. 102, Iss. 8 — 15 August 2020

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    • Figure 1
      Figure 1

      Rietveld analysis results of (a) Li0.5MoO2 and (b) LiMoO2, obtained at room temperature. In Li0.5MoO2 data, ∼27% of Li0.2MoO2 with a space group P21/c was identified as an impurity. Insets indicate the crystal structures. Dotted ovals indicate the preformed molybdenum dimers. Note that similar dimer patterns are realized in LiMoO2 and MoO2.

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    • Figure 2
      Figure 2

      (a) Average of the six Mo-O distances constituting the MoO6 octahedron. (b) Temperature dependence of x-ray diffraction patterns of LiMoO2. (c) X-ray appearance near-edge structure spectra for MoO2, Li0.5MoO2, and LiMoO2. (d) Mo-Mo distances consisting of preformed dimers.

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    • Figure 3
      Figure 3

      (a) Magnetic susceptibility for MoO2, Li0.5MoO2, and LiMoO2. H=1T was applied for collecting the data. For LiMoO2, the data was fitted by the white dotted line using the equation for isolated dimers [43]. (b) Li7-NMR spectra obtained at 200 K for magnetic fields of 2.0 and 4.0 T for LiMoO2. Δf is defined as the frequency shift measured from the reference frequency, Δf=f−γH. Inset shows the simulated pattern of typical powder patterns for −3/2↔−1/2 (red), 3/2↔1/2 (yellow), and −1/2↔1/2 (blue) when I=3/2. (c) Temperature dependencies on Li7-NMR spectra for LiMoO2. Inset shows the contour map of the intensity at various temperatures. (d) Spin-lattice relaxation rate (1/T1) and the Arrhenius plot with the function of 1/T1=aexp(−Δ/T) for LiMoO2. The inset shows the temperature dependence of the stretch exponent, β.

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    • Figure 4
      Figure 4

      The electronic structures of LiMoO2 and MoO2. (a)–(c) Schematics of the atomic orbitals composed of (a) σ, (b) π, and (c) δ bonds. (d), (e) Schematics of the energy levels of the molecular orbitals of a molybdenum dimer where the gap opens between the δ and δ* orbitals (d) but two nearly degenerate levels appear when the δ bonding is negligible (e). (f), (g) Calculated PDOSs for MoO2 (f) and LiMoO2 (g). (h) Calculated band dispersions (red lines) compared with the tight-binding band dispersions obtained using four dyz MLWFs (blue lines). GGA (U=0 eV) is used for the calculations in (f)–(h). (i) Intensity plot of the single-particle spectral function calculated by the DMFT where we assume U=1 eV.

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