Observation of Novel Liquid-Crystalline Phase Above the Bulk-Melting Temperature

In this paper, we show that a noncrystalline but ordered smectic-like phase exists above the bulk-melting temperature (T-m) at poly(n-alkyl acrylates)-air interface. The surface ordered phase is one monolayer thick and undergoes a sharp transition from order to disorder 10degreesC above T-m for n=22. The presence of a surface phase that does not exist in the bulk has important implications in the design of thermally responsive adhesives

A field induced modulated state in the ferromagnet PrPtAl

The theory of quantum order-by-disorder (QOBD) explains the formation of modulated magnetic states at the boundary between ferromagnetism and paramagnetism in zero field. PrPtAl has been argued to provide an archetype for this. Here, we report the phase diagram in magnetic field, applied along both the easy a axis and hard b axis. For field aligned to the b axis, we find that the magnetic transition temperatures are suppressed and at low temperature there is a single modulated fan state, separating an easy a axis ferromagnetic state from a field polarized state. This fan state is well explained with the QOBD theory in the presence of anisotropy and field. Experimental evidence supporting the QOBD explanation is provided by the large increase in the T^{2} coefficient of the resistivity and direct detection of enhanced magnetic fluctuations with inelastic neutron scattering, across the field range spanned by the fan state. This shows that the QOBD mechanism can explain field induced modulated states that persist to very low temperature

Synchrotron X-ray diffraction investigation of the surface condition of artefacts from King Henry VIII's warship the Mary Rose

Synchrotron X-ray diffraction (XRD) measured on the XMaS beamline at the ESRF was used to characterize the alloy composition and crystalline surface corrosion of three copper alloy Tudor artefacts recovered from the undersea wreck of King Henry VIII's warship the Mary Rose. The XRD method adopted has a dynamic range ∼1:105 and allows reflections <0.002% of the height of major reflections in the pattern to be discerned above the background without smoothing. Laboratory XRD, scanning electron microscopy–energy dispersive spectroscopy, synchrotron X-ray fluorescence and X-ray excited optical luminescence–X-ray near-edge absorption structure were used as supporting techniques, and the combination revealed structural and compositional features of importance to both archaeology and conservation. The artefacts were brass links believed to be fragments of chainmail and were excavated from the seabed during 1981 and 1982. Their condition reflects very different treatment just after recovery, viz. complete cleaning and conservation, chemical corrosion inhibition and chloride removal only, and distilled water soaking only (to remove the chlorides). The brass composition has been determined for all three at least in the top 7 µm or so as Cu(73%)Zn(27%) from the lattice constant. Measurement of the peak widths showed significant differences in the crystallite size and microstrain between the three samples. All of the links are found to be almost chloride-free with the main corrosion products being spertiniite, sphalerite, zincite, covellite and chalcocite. The balance of corrosion products between the links reflects the conservation treatment applied to one and points to different corrosion environments for the other two

Non-Fermi liquid behaviour below the Néel temperature in the frustrated heavy Fermion magnet UAu2

The term Fermi liquid is almost synonymous with the metallic state. The association is known to break down at quantum critical points (QCPs), but these require precise values of tuning parameters, such as pressure and applied magnetic field, to exactly suppress a continuous phase transition temperature to the absolute zero. Three-dimensional non-Fermi liquid states, apart from superconductivity, that are unshackled from a QCP are much rarer and are not currently well understood. Here, we report that the triangular lattice system uranium diauride (UAu(2)) forms such a state with a non-Fermi liquid low-temperature heat capacity [Formula: see text] and electrical resistivity [Formula: see text] far below its Néel temperature. The magnetic order itself has a novel structure and is accompanied by weak charge modulation that is not simply due to magnetostriction. The charge modulation continues to grow in amplitude with decreasing temperature, suggesting that charge degrees of freedom play an important role in the non-Fermi liquid behavior. In contrast with QCPs, the heat capacity and resistivity we find are unusually resilient in magnetic field. Our results suggest that a combination of magnetic frustration and Kondo physics may result in the emergence of this novel state

State of Ag in Pyrrhotite: Insights from X-ray Absorption Spectroscopy

Ag-bearing pyrrhotites Fe1-xS were synthesized by using the salt flux technique. The concentration of Ag in pyrrhotite reached 0.08 wt % at 540 °C and 1.3 wt % at 750-760 °C. The synthesized samples are divided into two groups according to the values of sulfur fugacity in the experimental system and the content of Fe (CFe) in pyrrhotite. In group (i) at low sulfur fugacity (log f(S2) ≈ −6.5, CFe > 48.8 at. %), Ag is disseminated in pyrrhotites in an “invisible” form but mostly concentrates on the grain boundaries of crystals as metallic rims. In group (ii) at high sulfur fugacity (log f(S2) ≈ −1.0, CFe < 48.8 at. %), Ag occurs as an invisible form disseminated in the pyrrhotite matrix together with the minor form of Ag-bearing submicron inclusions. Analysis of Ag K-edge XAS spectra recorded at ambient temperature revealed that the samples of group (i) contain a small fraction of the invisible Ag+ form, while the majority of Ag presents in pyrrhotite crystals as Ag°. The samples of group (ii) at a temperature of 750 °C contain the invisible form of Ag-Ag2+S-like clusters. The decrease in temperature leads to the partial decomposition of the invisible form and the appearance of the second (minor) form, Ag-bearing submicron inclusions. The predicted concentrations of Ag in pyrrhotite coincide with those from natural samples of various origins