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We have observed dynamical diffraction in the $[[\left(0240\overline{2}4\right)$ and $[[\left(0460\overline{4}6\right)$ reflections of the icosahedral quasicrystal AlPdMn in the back-reflection geometry ( ${\ensuremath{\theta}}_{B}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}90\ifmmode^\circ\else\textdegree\fi{}$). The x-ray fluorescence from the Al and Pd atoms exhibits strong standing wave behavior, similar to that observed in crystalline materials. The data indicate a long-range order of each species of atoms, with the coherent positions attributable to distributions of the Al and Pd, which we compare to a centrosymmetric model. We observe deviations from the model which imply small departures from inversion symmetry along the twofold symmetry axis and from the expected coherent fractions for Al.

Electrical resistivity and magnetic susceptibility measurements of the itinerant ferromagnet ${\mathrm{CoS}}_{2}$ at high pressures reveal that its magnetic ordering temperature is tuned to zero at a critical pressure 4.8 GPa, indicating the existence of a quantum-phase transition. The ambient pressure continuous magnetic-phase transition in ${\mathrm{CoS}}_{2}$ becomes first order on a very slight pressure increase, with a tricritical point probably located almost at ambient pressure. No deviations from Fermi-liquid behavior were found in the vicinity of the quantum-phase transition in ${\mathrm{CoS}}_{2}$, implying its strong first-order nature.

Recent work on the growth of thin metal films on quasicrystalline substrates has indicated the formation of so-called “magic height” islands with multiples of 4 atomic layers (AL) arising as a result of quantum size effects, which lead to enhanced stability. Here the results of a study are reported of Bi deposition on i-Al-Pd-Mn using medium-energy ion scattering to characterize the island thickness and the structural arrangement of Bi atoms within the islands. In addition, data were taken from annealed surfaces after Bi cluster desorption to leave a single aperiodic monolayer of Bi at the surface. Scattered-ion energy spectra from the Bi islands are consistent with a single Bi monolayer covered with mainly 4 AL islands for both 1.8 and 3.2 monolayer equivalent coverages but with some occupation of 2 and 8 Al islands as well. The angular dependence of the scattered-ion intensity (“blocking curve”) from Bi has been compared with simulations for various models of both rhombohedral Bi and a distorted “black-phosphorus”-like structure. The data demonstrate bilayer formation within the Bi islands. In the case of the aperiodic Bi monolayer, the blocking curves from substrate scattering are found to be inconsistent with two high-symmetry sites on the quasicrystalline surface that theory indicates are energetically favorable but do not exclude the formation of pentagonal arrangements of Bi atoms as seen in other recent experimental work.

Using electron diffraction, we show that free-electron metals, such as sodium and potassium, form a highly regular quasiperiodic monolayer on the fivefold surface of icosahedral Al-Pd-Mn and that the quasiperiodicity propagates up to the second layer in sodium. Our photoelectron spectroscopy results show that the quasicrystalline alkali-metal adlayer does not exhibit a pseudogap near the Fermi level thought to be characteristic for the electronic structure of quasicrystalline materials. Calculations based on density functional theory provide a model structure for the quasicrystalline alkali-metal monolayer and confirm the absence of a pseudogap.

${\mathrm{Ti}}_{50}{\mathrm{Pd}}_{50\ensuremath{-}x}{\mathrm{Cr}}_{x}$ is a high-temperature shape-memory alloy with a martensitic transformation temperature strongly dependent on the Cr composition. Prior to the transformation, a premartensitic phase is present with an incommensurate modulated cubic lattice with wave vector of ${q}_{0}=(0.22,0.22,0)$. The temperature dependence of the diffuse scattering in the cubic phase is measured as a function temperature for $x=6.5$, 8.5, and $10\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$. The lattice dynamics has been studied and reveals anomalous temperature and $q$ dependences of the $[110]\text{\ensuremath{-}}{\mathrm{TA}}_{2}$ transverse phonon branch. The phonon linewidth is broad over the entire Brillouin zone and increases with decreasing temperature, contrary to the behavior expected for anharmonicity. No anomaly is observed at ${q}_{0}$. The results are compared with first principles calculation of the phonon structure.

A careful study of thermodynamic and transport properties of a high-quality single crystal of $\mathrm{MnSi}$ at ambient pressure suggests that its transition to a helical magnetic state near $29\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ is weakly first order. The heat capacity, temperature derivative of resistivity, thermal expansion, and magnetic susceptibility exhibit a specific structure around the phase transition point, interpreted as a combination of first- and second-order features. Striking mirror symmetry between the temperature derivative of resistivity and the thermal expansion coefficient is observed. Conclusions drawn from these experiments question prevailing views on the phase diagram of $\mathrm{MnSi}$.

The elucidation of the local atomic structure of a pseudomorphic film of Cu deposited on the five-fold surface of $i\text{\ensuremath{-}}{\mathrm{Al}}_{70}{\mathrm{Pd}}_{21}{\mathrm{Mn}}_{9}$ using medium-energy ion scattering spectroscopy is reported. Monte Carlo calculations, using the VEGAS code, have been utilized to simulate the blocking of $100\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ ${\mathrm{He}}^{+}$ ions scattered from the overlayer. The coordinates of the Cu atoms in the overlayer derived from this procedure are consistent with a structure occurring in five rotational domains. Each domain consists of nanoscale strips of fcc $\mathrm{Cu}(100)$ with the $⟨110⟩$ azimuth aligned along the five-fold directions of the quasicrystalline substrate. The strips are arranged according to a one-dimensional Fibonacci sequence with long and short widths related by the golden mean $\ensuremath{\tau}$. Upon annealing the film transforms to an alloyed structure composed of five orientational domains of fcc material with the (110) axis perpendicular to the surface.