We present an ionothermal-based method for the simple and low-cost enrichment in 17 O of oxide materials. This is demonstrated for the case of SIZ-4, an ionothermally-prepared aluminophosphate framework with the CHA topology. A preliminary study of unenriched samples of SIZ-4 highlights the importance of the careful choice of template in order to obtain an ordered structure. We then show how an ionothermal synthesis procedure incorporating microlitre quantities of 17 O-enriched H 2 O enables asprepared and calcined samples of SIZ-4 to be obtained with 17 O enrichment levels that are sufficient to enable the recording of high-quality 17 O solid-state NMR spectra. While second-order quadrupolarbroadened resonances are unresolved in 17 O MAS NMR spectra, 17 O double-rotation (DOR) and multiple-quantum (MQ)MAS NMR spectra reveal distinct resonances that are partially assigned by comparison with NMR parameters derived using first-principles calculations. The calculations also enable an investigation of the dependence of 17 O NMR parameters on the local structural environment. We find that both the 17 O isotropic chemical shift and quadrupolar coupling constant show clear dependencies on Al-O-P bond lengths, and angles and will therefore provide a sensitive probe of structure and geometry in aluminophosphate frameworks in future studies.

The vanadium oxyfluoride [NH(4)](2)[C(7)H(14)N][V(7)O(6)F(18)] (DQVOF) is a geometrically frustrated magnetic bilayer material. The structure consists of S = 1/2 kagome planes of V(4+) d(1) ions with S = 1 V(3+) d(2) ions located between the kagome layers. Muon spin relaxation measurements demonstrate the absence of spin freezing down to 40 mK despite an energy scale of 60 K for antiferromagnetic exchange interactions. From magnetization and heat capacity measurements we conclude that the S = 1 spins of the interplane V(3+) ions are weakly coupled to the kagome layers, such that DQVOF can be viewed as an experimental model for S = 1/2 kagome physics, and that it displays a gapless spin liquid ground state.

The presence and thermal stability of anion order in the oxynitride perovskites SrTaO 2 N and LaTaON 2 have been determined using high resolution powder neutron and electron diffraction data. Partial order of oxide and nitride anions consistent with the formation of planes of disordered cis-anion chains is observed in both materials, with a chemical symmetry between distributions in SrTaO 2 N and LaTaON 2 . No loss of anion order is observed up to 1100 °C and extrapolations based on lattice strains show the order to be stable to remarkably high temperatures >2000 °C, demonstrating that anions are segregated when the materials are synthesized. SrTaO 2 N has an apparent tetragonal I4/mcm superstructure at room temperature due to ordered octahedral tilts, but anion order lowers symmetry to an orthorhombic Fmmm supercell (with lattice parameters a = 8.0657( 8), b = 8.0614(7), and c = 8.0775(4) Å). Anion order also lowers the symmetry of LaTaON 2 from apparent orthorhombic Imma to monoclinic I2/m (a = 5.7140( 6), b = 8.0595(6), c = 5.7506(5) Å, and β = 90.239(4)°at 20 °C) and this superstructure persists up to 1100 °C with an extrapolated loss of tilting at 1540 °C. Anion order appears to direct octahedral tilting such that the more rigid Ta−N−Ta bridges retain bond angles closer to 180°than the Ta− O−Ta connections in these superstructures.

We present new magnetic heat capacity and neutron scattering results for two magnetically frustrated molybdate pyrochlores: S=1 oxide Lu_{2}Mo_{2}O_{7} and S=1/2 oxynitride Lu_{2}Mo_{2}O_{5}N_{2}. Lu_{2}Mo_{2}O_{7} undergoes a transition to an unconventional spin glass ground state at T_{f}∼16  K. However, the preparation of the corresponding oxynitride tunes the nature of the ground state from spin glass to quantum spin liquid. The comparison of the static and dynamic spin correlations within the oxide and oxynitride phases presented here reveals the crucial role played by quantum fluctuations in the selection of a ground state. Furthermore, we estimate an upper limit for a gap in the spin excitation spectrum of the quantum spin liquid state of the oxynitride of Δ∼0.05  meV or Δ/|θ|∼0.004, in units of its antiferromagnetic Weiss constant θ∼-121  K.

Spin liquid ground states are predicted to arise within several distinct scenarios in condensed matter physics. The observation of these disordered magnetic states is particularly pervasive amongst a class of materials known as frustrated magnets, in which the competition between various magnetic exchange interactions prevents the system from adopting long-range magnetic order at low temperatures. Spin liquids continue to be of great interest due to their exotic nature and the possibility that they may support fractionalised excitations, such as Majorana fermions. Systems that allow for such phenomena are not only fascinating from a fundamental perspective but may also be practically significant in future technologies based on quantum computation. Here we show that the underlying antiferromagnetic sublattice in TbInO3 undergoes a crystal field induced triangular-to-honeycomb dilution at low temperatures. The absence of a conventional magnetic ordering transition at the lowest measurable temperatures indicates that another critical mechanism must govern in the ground state selection of TbInO3. We propose that anisotropic exchange interactionsmediated through strong spin-orbit coupling on the emergent honeycomb lattice of TbInO3give rise to a highly frustrated spin liquid.One notable example of a spin liquid 1,2 is that of the S = ½ Heisenberg antiferromagnet on a two-dimensional kagome lattice, a frustrated network of corner-sharing triangles. It is now widely considered that this magnetic system displays a quantum spin liquid ground state 3 and there is recent experimental evidence to suggest that a gapped quantum spin liquid state is likely realised in the Cu 2+ -based kagome antiferromagnet, herbertsmithite. 4 The two-dimensional honeycomb net, on the other hand, is a bipartite lattice and, therefore, does not give rise to frustrated ground states in the presence of conventional nearest-