Measurements of the electrical resistivity, magnetoresistance, ac and dc magnetic susceptibility and specific heat on YbBiPt indicate this compound to be a IveryP heavy-electron system. The low-temperature Sommerfeld coefficient of 8 J/${\mathrm{K}}^2$ (mole Yb) is not affected by a phase transition at 0.4 K. We suggest that the heavy-mass state in YbBiPt is unconventional in that it develops from Bloch states in an electronic subsystem with low carrier concentration.

We report on the effect of grain size on the ionic conductivity of yttria-stabilized zirconia samples synthesized by ball milling. Complex impedance measurements, as a function of temperature and frequency are performed on 10$\hskip0.3em${}mol\,% yttria-stabilized zirconia nanocrystalline samples with grain sizes ranging from 900 to 17 nm. Bulk ionic conductivity decreases dramatically for grain sizes below 100 nm, although its activation energy is essentially independent of grain size. The results are interpreted in terms of a space-charge layer resulting from segregation of mobile oxygen vacancies to the grain-boundary core. The thickness of this space-charge layer formed at the grain boundaries is on the order of 1 nm for large micron-sized grains but extends up to 7 nm when decreasing the grain size down to 17 nm. This gives rise to oxygen vacancies depletion over a large volume fraction of the grain and consequently to a significant decrease in oxide-ion conductivity.

The structure of high quality $[{\mathrm{YBCO}}_N/{\mathrm{PBCO}}_M{]}_{1000Å}$ superlattices, with $N$ ranging between 1 and 12 unit cells and $M=5\mathrm{}$ unit cells, grown by high oxygen pressure sputtering, is analyzed. Intracell atomic structure of the layers along the $c$ axis and disorder at interfaces is investigated using an x-ray refinement technique. Negligible roughness, step disorder, and interdiffusion are found at the interfaces. Epitaxial mismatch strain results in a surprising reorganization of interatomic distances for the thinnest YBCO layers, which seems to correlated with the decrease in the critical temperature. Intracell structure is invoked as an additional source of $T_c$ changes in very thin YBCO layers.

The presence of organic ligands on the surface of colloidal nanoparticles strongly limits their performance in technological applications where charge carrier transfer/transport plays an important role. We use metal salts, matched with the nanoparticle composition, to eliminate the surface organic ligands without introducing extrinsic impurities in the final nanomaterial. The potential of the simple, general and scalable processes presented here is demonstrated by characterizing the thermoelectric properties of nanostructured Ag₂Te produced by the bottom up assembly of Ag₂Te nanocrystals. A 6-fold increase of the thermoelectric figure of merit of Ag₂Te was obtained when organic ligands were displaced by AgNO₃. The same procedure can enhance the performance of nanocrystals and nanocrystal-based devices in a broad range of applications, from photovoltaics and thermoelectrics to catalysis.

Current-voltage $\mathrm{}(I-V)\mathrm{}$ characteristics were used to investigate the response of the vortex-glass (VG) phase transition in high-quality epitaxial ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ films in magnetic fields up to 7 T. We show that varying the oxygen content, the scaling analysis reveals a crossover from three-dimensional (3D) to a pure 2D VG transition with $T_g=0.\mathrm{}$ At small oxygen deficiencies $(7\mathrm{}-\delta =6.75),$ the $\rho -j$ curves scale according to the 3D VG model, which cannot be distinguished from a Bose-glass model from a scaling analysis with the magnetic field applied parallel to the c axis. At a lower oxygen content $(7\mathrm{}-\delta =6.48),$ the VG phase transition behaves analogous to the highly anisotropic ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_8$ samples, showing a quasi-2D VG transition. For further deoxygenated samples $(7\mathrm{}-\delta =6.4),$ the result is consistent with a pure 2D vortex-glass model similar to that observed in the even more anisotropic ${\mathrm{Tl}}_2{\mathrm{Ba}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_8$ thin films. The estimated value of the anisotropy in high-quality oxygen-depleted samples is comparable to that of the highly anisotropic superconductors.

We report on the magnetic properties of mechanically alloyed ${\mathrm{Al}}_{49}{\mathrm{Fe}}_{30}{\mathrm{Cu}}_{21}.$ The system was observed by high-resolution electron microscopy to be composed of nanosized solid solution grains embedded in an amorphous matrix of roughly the same composition. The irreversibility between the field-cooled and zero-field-cooled magnetization curves together with some ac susceptibility features closely resemble those exhibited by spin glasses. However, the analysis of the nonlinear susceptibility allowed us to rule out the existence of a true thermodynamic phase transition, since it was apparent the absence of a divergent increase in the nonlinear coefficients on approaching the freezing temperature. Surface effects are considered a minor source for the observed phenomena, remaining the blocking of interacting superparamagnetic moments the main mechanism to account for them. We discuss these three different origins for spin-glass-like behavior in the context of mechanically alloyed materials.