Electrical resistivity ρ(T) and specific heat C(T) measurements have been made on the diluted 4f2 system Y(Pr)Ir2Zn20. Both data of ρ and magnetic specific heat Cm per Pr ion are well scaled as a ...function of T/T0, where T0 is a characteristic temperature of non-Fermi-liquid (NFL) behaviors. Furthermore, the temperature dependences of ρ and Cm/T agree with the NFL behaviors predicted by the two-channel Kondo model for the strong coupling limit. Therefore, we infer that the observed NFL behaviors result from the single-site quadrupole Kondo effect due to the hybridization of the 4f2 states with multichannel conduction electrons.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
CeIrSn with a quasikagome Ce lattice in the hexagonal basal plane is a strongly valence fluctuating compound, as we confirm by hard x-ray photoelectron spectroscopy and inelastic neutron scattering, ...with a high Kondo temperature of TK ∼ 480 K. We report a negative in-plane thermal expansion α/T below 2 K, which passes through a broad minimum near 0.75 K. Volume and a -axis magnetostriction for B ∥ a are markedly negative at low fields and change sign before a sharp metamagnetic anomaly at 6 T. These behaviors are unexpected for Ce-based intermediate valence systems, which should feature positive expansivity. Rather they point towards antiferromagnetic correlations at very low temperatures. This is supported by muon spin relaxation measurements down to 0.1 K, which provide microscopic evidence for a broad distribution of internal magnetic fields. Comparison with isostructural CeRhSn suggests that these antiferromagnetic correlations emerging at T ≪ TK result from geometrical frustration.
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A field survey team went to Palu City, Indonesia in the aftermath of the September 28th, 2018 earthquake and tsunami to investigate its effects on local infrastructure and buildings. The study ...focused on the coast of Palu Bay, where a tsunami wave between approximately 2 and 7 m high impacted the local community as a result of several complex tsunami source mechanisms. The following study outlines the results, focused on loading caused by debris entrained within the inundating flow. Damage to timber buildings along the coast was widespread, though reinforced concrete structures for the most part survived, providing valuable insights into the type of debris loads and their effects on structures. The results of this survey are placed within the context of Canadian tsunami engineering challenges and are compared to the recently-released ASCE 7 Chapter 6 – Tsunami Loads and Effects, detailing potential research gaps and needs.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We performed inelastic neutron scattering experiments on PrMgNi4 with the cubic MgSnCu4-type structure. The magnetic excitations were observed at 1.1, 2.5, 5.9, 10.7, and 11.7 meV. Since the energy ...of the excitations is constant for |Q| < 5 Å−1, they are ascribed to the crystalline electric field (CEF) excitations of the Pr3+ ions. We adopted CEF parameters of W = −3.3 K and x = 0.8 for the cubic Td point group to reproduce the strong excitations at 1.1, 10.7, and 11.7 meV. The calculated CEF level scheme reveals the Γ3 doublet ground state with the quadrupolar degrees of freedom and the excited states of Γ4 triplet (1.4 meV), Γ1 singlet (3.4 meV), and Γ5 triplet (13.5 meV). This scheme, however, does not explain the observed two excitations at 2.5 and 5.9 meV. These additional excitations may arise from splitting of the doublet by symmetry lowering due to excess Mg atoms occupying the Pr sites. This splitting is probably responsible for the absence of the long-range quadrupole order in PrMgNi4.
► Single crystals of type-VIII clathrate Ba8Ga16Sn30 doped with Cu were grown. ► The size of p-type single crystals is twice as large as that grown without Cu. ► The thermoelectric figure of merit ZT ...was assessed for 300⩽T⩽600 K. ► The ZT values of the p- and n-type crystals reach 0.88 and 1.45, respectively.
The intermetallic clathrate Ba8Ga16Sn30 with type-VIII structure is one of the promising thermoelectric materials. We report on significant effects of Cu doping on both the crystal growth and thermoelectric properties of type-VIII clathrate Ba8Ga16Sn30. By using the Ga flux and Sn flux, respectively, the carrier type could be tuned as p- and n-types. The p-type single crystals were grown to approximately 6mm in diameter, which is twice as large as that grown without Cu. The crystals were characterized by electron-probe microanalysis and powder X-ray diffraction and used for the measurements of the electrical resistivity, Seebeck coefficient, and thermal conductivity. The values of the dimensionless figure of merit ZT of the p- and n-type crystals reached 0.88 and 1.45 at around 500K, respectively, the latter of which is the highest among all substituted systems of type-VIII Ba8Ga16Sn30. This enhancement of ZT is discussed in relation with the charge balance and modification of the band structure caused by Cu doping.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Powder neutron diffraction measurements were carried out to investigate the magnetic structure of the antiferromagnet NdRh2Zn20. The magnetic reflections observed for T ≤ 1.0 K are indexed by the ...propagation vector of k = (1/2, 1/2, 1/2). From the analysis of the intensity of magnetic reflections, a magnetic structure described by the Γ6 representation is proposed. The magnetic moments are parallel to the 112¯ or 1¯10 direction and stacked with a sequence of up-up-down-down along the 111 direction.
CePt6Al3 is a rare example of the Ce-based honeycomb lattice compound. Substitution of the isovalent Pt for Pd transforms the ground state from a paramagnetic heavy-fermion state to an ...antiferromagnetic (AFM) ordered state. To gain insight into the role of magnetic frustration in the honeycomb Kondo lattice, we have measured the magnetization M(B) and electrical resistivity ρ(B) of Ce(Pt1-xPdx)6Al3 (x ≤ 0.3) in pulsed magnetic fields up to 60 T. For the single crystal with x = 0, M(B) for B along the easy c axis exhibits a metamagnetic increase and ρ(B || c) bends at Bm = 28 T. Taking the temperature at a shoulder in the magnetic susceptibility χ(ल) for B ‖ c as Tχm = 17 K, the ratio μBBm/KBT>χm is estimated to be 1.1. This value agrees with those reported for Ce-based paramagnetic heavy-fermion compounds with similar magnitudes of Bm. With increasing x from 0 to 0.3 in polycrystalline samples, the magnitude of M(B = 60 T) at 1.4 K increases from 0.75 to 2.0 μβ/Ce, indicating the recovery of localized 4f moments by the Pd substitution for Pt. Using the data of M(B) and ρ(B) for x = 0.1, 0.2, 0.3, we constructed B-T phase diagrams, which show a trend from a small moment AFM ordered state for x = 0.1 to a large moment AFM ordered state for x = 0.3.
X-ray diffraction and inelastic x-ray scattering measurements of liquid Ba8Ga16Sn30 have been carried out to investigate local structure and atomic dynamics in the liquid. The pair distribution ...function shows shorter and longer interatomic distances in the first coordination shell. The dynamic structure factor exhibits the inelastic excitations on both sides of the quasielastic central peak. The inelastic excitations disperse with increasing the momentum transfer, suggesting the longitudinal acoustic mode. We found a low energy excitation in addition to the longitudinal acoustic excitation in the dynamic structure factor and it reminds us a strong relationship with a rattling motion of a guest (Ba) atom in the solid state. The temperature dependence of the pair distribution function and the longitudinal acoustic excitation energy is very weak in a range from 600 to 900 °C. The result suggests that Ba and other atoms in the melt are located around minimum positions of the effective pair potential approximated as a harmonic one.
In an antiferromagnetic zigzag chain, competition between the nearest and next-nearest neighbor interactions could give rise to magnetic frustration. Magnetic semiconductors RAgSe2 (R = Ho, Er, Tm, ...and Yb) crystallize in the ErAgSe2-type orthorhombic structure, where the R ions form a zigzag chain along the orthorhombic a-axis. The magnetic susceptibility data for all the samples follow the Curie-Weiss law between 40 and 300 K. The values of the effective magnetic moment μβα are close to those expected for the free R3+ ions. Negative values of the paramagnetic Curie temperature θρ indicate antiferromagnetic interactions. For R = Ho and Tm, the specific heat C(T) data exhibit no anomaly down to 0.4 K, which is ascribed to the nonmagnetic singlet ground states under the crystalline electric fields. On the other hand, for R = Er, C(T) shows peaks at T1 = 1.3 K and T2 = 0.9 K, indicating successive antiferromagnetic transitions. For R = Yb, C(T) shows a lambda-type anomaly at Tm = 1.8 K. The magnetic entropy at Tm is only 30% of Rln2 expected for the ground state doublet, suggesting magnetic fluctuations above Tm.
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