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Polycrystalline LiMo8O10 was prepared in a sealed Mo crucible at 1380 °C for 48 h using the conventional high-temperature solid-state method. The polar tetragonal crystal structure (space group I41md) is confirmed based on the Rietveld refinement of powder neutron diffraction and 7Li/6Li solid-state NMR. The crystal structure features infinite chains of Mo4O5 (i.e., Mo2Mo4/2O6/2O6/3) as a repeat unit containing edge-sharing Mo6 octahedra with strong Mo–Mo metal bonding along the chain. X-ray absorption near-edge spectroscopy of the Mo-L3 edge is consistent with the formal Mo valence/configuration. Magnetic measurements reveal that LiMo8O10 is paramagnetic down to 1.8 K. Temperature-dependent resistivity [ρ(T)] measurement indicates a semiconducting behavior that can be fitted with Mott’s variable range hopping conduction mechanism in the temperature range of 215 and 45 K. The ρ(T) curve exhibits an exponential increase below 5 K with a large ratio of ρ1.8/ρ300 = 435. LiMo8O10 shows a negative field-dependent magnetoresistance between 2 and 25 K. Heat capacity measurement fitted with the modified Debye model yields the Debye temperature of 365 K.more » « less
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The leading order nonlinear (NL) susceptibility, χ3, in a paramagnet is negative and diverges as T → 0. This divergence is destroyed when spins correlate and the NL response provides unique insights into magnetic order. Dimensionality, exchange interaction, and preponderance of quantum effects all imprint their signatures in the NL magnetic response. Here, we study the NL susceptibilities in the proximate Kitaev magnet α-RuCl3, which differs from the expected antiferromagnetic behavior. For T < Tc = 7.5 K and field B in the ab-plane, we obtain contrasting NL responses in low (<2 T) and high field regions. For low fields, the NL behavior is dominated by a quadratic response (positive χ2), which shows a rapid rise below Tc. This large χ2 > 0 implies a broken sublattice symmetry of magnetic order at low temperatures. Classical Monte Carlo (CMC) simulations in the standard K − H − Γ model secure such a quadratic B dependence of M, only for T ≈ Tc with χ2 being zero as T → 0. It is also zero for all temperatures in exact diagonalization calculations. On the other hand, we find an exclusive cubic term (χ3) that describes the high field NL behavior well. χ3 is large and positive both below and above Tc crossing zero only for T > 50 K. In contrast, for B ∥ c-axis, no separate low/high field behaviors are measured and only a much smaller χ3 is apparent.more » « less