The in situ high-pressure phase transition behaviors of energetic material 4-carboxybenzenesulfonyl azide (C7H5N3O4S, 4-CBSA) have been investigated by the measurements of Raman scattering, mid-IR absorption, and angle-dispersive X-ray diffraction (ADXRD) in diamond anvil cells, the highest pressure in our studies was up to ∼14.6 GPa at room temperature. 4-CBSA transforms from phase I into phase II around 0.5–0.9 GPa, and then starts to going to phase III at about 2.5 GPa, phase II coexists with phase III until to about 5.5 GPa, the phase III of 4-CBSA finally begins to transform into amorphous state above 10.5 GPa. The first phase transition (phase I–II) of 4-CBSA is induced by the change of molecular conformation, and the second phase transition (phase II–III) is attributed to the distortion of benzene ring and the change of intermolecular O–H···O hydrogen bonds. The existence of sulfonyl group makes it much easier for the bent azide group to decompose under high pressure, which interpret that the amorphization pressure in 4-CBSA is much lower than that in benzyl azide. The unique behavior of the azide group may be helpful to understand the electron orbit hybridization and the formation of polymeric nitrogen.
A quantum spin liquid (QSL) is an exotic state in which electron spins are highly entangled, yet keep fluctuating even at zero temperature. Experimental realization of model QSLs has been challenging due to imperfections, such as antisite disorder, strain, and extra or a lack of interactions in real materials compared to the model Hamiltonian. Here we report the magnetic susceptibility, thermodynamic, inelastic neutron scattering (INS), and muon-spin relaxation studies on a polycrystalline sample of PrZnAl 11 O 19 , where the Pr 3+ ions form an ideal two-dimensional triangular lattice. Our results demonstrate that this system does not order nor freeze, but keeps fluctuating down to 50 mK despite large antiferromagnetic couplings (∼ − 10 K). Furthermore, the INS and specific-heat data suggest that PrZnAl 11 O 19 is best described as a gapless QSL.
Monoclinic Li3Co2SbO6 has been proposed as a Kitaev spin liquid candidate and investigated intensively, whereas the properties of its polymorph, the orthorhombic phase, are less known. Here we report the magnetic properties of orthorhombic Li3Co2SbO6 as revealed by dc and ac magnetic susceptibility, muon spin relaxation (μSR), and neutron diffraction measurements. Successive magnetic transitions at 115, 89, and 71 K were observed in the low-field dc susceptibility measurements. The transitions below T N (115 K) are suppressed at higher applied fields. However, zero-field ac susceptibility measurements reveal distinct frequency-independent transitions at about 114, 107, 97, 79, and 71 K. A long-range magnetic ordered state was confirmed by specific heat, μSR, and neutron diffraction measurements, all indicating a single transition at about 115 K. The discrepancy between different measurements is attributed to possible stacking faults and/or local disorders of the ferromagnetic zigzag chains, resulting in ferromagnetic boundaries within the overall antiferromagnetic matrix.
Rhodium-containing compounds offer a fertile playground to explore novel materials with superconductivity and other fantastic electronic correlation effects. A new ternary rhodium-antimonide La2Rh3+δSb4(δ ≈ 1/8) has been synthesized by a Bi-flux method. It crystallizes in the orthorhombic Pr2Ir3Sb4-like structure, with space group Pnma (No. 62). The crystalline structure appears as stacking the two dimensional RhSb4- and RhSb5-polyhedra networks along b axis, and the La atoms embed in the cavities of these networks. Band structure calculations confirm it as a multi-band metal with a van-Hove singularity like feature at the Fermi level, whose density of states are mainly of Rh-4d and Sb-5p characters. The calculations also implies that the redundant Rh acts as charge dopant. Superconductivity is observed in this material with onset transition at Ton c ≈ 0.8 K. Ultra-low temperature magnetic susceptibility and specific heat measurements suggest that it is an s-wave type-II superconductor. Our work may also imply that the broad Ln 2 Tm 3+δSb4(Ln=Rare earth, Tm=Rh, Ir...) family may host new material bases where new superconductors, quantum magnetism and other electronic correlation effects could be found.
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