17 research outputs found
Spatially anisotropic S=1 square-lattice antiferromagnet with single-ion anisotropy realized in a Ni(II) pyrazine- n,n′ -dioxide coordination polymer
The Ni(NCS)2(pyzdo)2 coordination polymer is found to be an S=1 spatially anisotropic square lattice with easy-axis single-ion anisotropy. This conclusion is based upon considering in concert the experimental probes x-ray diffraction, magnetic susceptibility, magnetic-field-dependent heat capacity, muon-spin relaxation, neutron diffraction, neutron spectroscopy, and pulsed-field magnetization. Long-range antiferromagnetic (AFM) order develops at TN=18.5K. Although the samples are polycrystalline, there is an observable spin-flop transition and saturation of the magnetization at ≈80T. Linear spin-wave theory yields spatially anisotropic exchanges within an AFM square lattice, Jx=0.235meV, Jy=2.014meV, and an easy-axis single-ion anisotropy D=-1.622meV (after renormalization). The anisotropy of the exchanges is supported by density functional theory
Spatially anisotropic S=1 square-lattice antiferromagnet with single-ion anisotropy realized in a Ni(II) pyrazine-n, n'-dioxide coordination polymer
Nafion® as advanced immobilisation substrate for the voltammetric analysis of electroactive microparticles: the case of some artistic colouring agents
Voltammetry of microparticles is applied to characterise
and to identify solid analytes of interest in the field
of cultural heritage. Nafion® is used for the immobilisation
of solid microparticles onto the surface of a glassy carbon
electrode by exploiting the deposition onto the electrode
surface of a micro-volume of a suspension of the microsample
in polymeric solution. Cyclic voltammetry and
square wave voltammetry are applied to characterise and
to identify the microparticles immobilised in the Nafion®
coating. The analyte studied in this work is Prussian Blue as
a typical inorganic pigment, with a relatively simple electrochemical
behaviour. The proposed method is applied to a
sample of Venetian marmorino plaster. The performance of
Nafion® for this analysis is compared with that of the
polymer Paraloid B72
Recommended from our members
Coexistence of superconductivity and short-range double-stripe spin correlations in Te-vapor annealed FeTe1-xSex (x≤0.2) COEXISTENCE of SUPERCONDUCTIVITY and SHORT- ⋯ ZHIJUN XU et al.
In as-grown bulk crystals of Fe1+yTe1-xSex with x≲0.3, excess Fe (y>0) is inevitable and correlates with a suppression of superconductivity. At the same time, there remains the question as to whether the character of the antiferromagnetic correlations associated with the enhanced anion height above the Fe planes in Te-rich samples is compatible with superconductivity. To test this, we have annealed as-grown crystals with x=0.1 and 0.2 in Te vapor, effectively reducing the excess Fe and inducing bulk superconductivity. Inelastic neutron scattering measurements reveal low-energy magnetic excitations consistent with short-range correlations of the double-stripe type; nevertheless, cooling into the superconducting state results in a spin gap and a spin resonance, with the extra signal in the resonance being short range with a mixed single-stripe/double-stripe character, which is different than other iron-based superconductors. The mixed magnetic character of these superconducting samples does not appear to be trivially explainable by inhomogeneity
Spatially anisotropic S=1 square-lattice antiferromagnet with single-ion anisotropy realized in a Ni(II) pyrazine-n, n'-dioxide coordination polymer
Recommended from our members
Witnessing quantum criticality and entanglement in the triangular antiferromagnet KYbSe
The Heisenberg triangular lattice quantum spin liquid and the phase
transitions to nearby magnetic orders have received much theoretical attention,
but clear experimental manifestations of these states are rare. This work
investigates a new spin-half Yb delafossite material, KYbSe, whose
inelastic neutron scattering spectra reveal a diffuse continuum with a sharp
lower bound. Applying entanglement witnesses to the data reveals multipartite
entanglement spread between its neighbors, and analysis of its magnetic
exchange couplings shows close proximity to the triangular lattice Heisenberg
quantum spin liquid. Key features of the data are reproduced by Schwinger-boson
theory and tensor network calculations with a significant second-neighbor
coupling . The strength of the dynamical structure factor at the point
shows a scaling collapse in down to 0.3 K,
indicating a second-order quantum phase transition. Comparing this to previous
theoretical work suggests that the proximate phase at larger is a gapped
spin liquid, resolving a long-debated issue. We thus show that
KYbSe is close to a spin liquid phase, which in turn sheds light on the
theoretical phase diagram itself
Strong cooperative coupling of pressure-induced magnetic order and nematicity in FeSe
A hallmark of the iron-based superconductors is the strong coupling between
magnetic, structural and electronic degrees of freedom. However, a universal
picture of the normal state properties of these compounds has been confounded
by recent investigations of FeSe where the nematic (structural) and magnetic
transitions appear to be decoupled. Here, using synchrotron-based high-energy
x-ray diffraction and time-domain Moessbauer spectroscopy, we show that
nematicity and magnetism in FeSe under applied pressure are indeed strongly
coupled. Distinct structural and magnetic transitions are observed for
pressures, 1.0 GPa <= p <= 1.7 GPa, which merge into a single first-order phase
line for p >= 1.7 GPa, reminiscent of what has been observed, both
experimentally and theoretically, for the evolution of these transitions in the
prototypical doped system, Ba(Fe[1-x]Co[x])2As2. Our results support a
spin-driven mechanism for nematic order in FeSe and provide an important step
towards a universal description of the normal state properties of the
iron-based superconductors.Comment: (14 pages, 4 figures