We have measured the melting temperature of nanoscale indium islands on a WSe(2) substrate using perturbed angular correlations combined with scanning tunneling microscopy. The indium islands are self-assembled nanostructures whose diameter can vary between about 5 and 100 nm, depending on deposition conditions. The melting point decreases due to surface energies as the islands get smaller. This decrease depends on the faceting of the crystalline nanostructures and interactions between the islands and the substrate.

Perturbed angular correlation spectra of y-rays emitted following the decay of dilute lS1Hf in several zirconia ceramics are reported. Spectra for monoclinic and tetragonal zirconia, a tetragonal zirconidyttria alloy, a cubic zirconidyttria alloy, and two mixed tetragonallcubic-phase zirconidyttria alloys were measured as a function of temperature to 1470OC. The spectrum observed for each phase has a unique signature, and the spectrum of mixed-phase materials can be used to determine the relative amounts of the different phases. These data give a cubic/(cubic + tetragonal) phase boundary that is somewhat lower in temperature than indicated by current phase diagrams.

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We have measured the temperature dependence of the electric and magnetic hyperfine interactions at 181 Ta nuclei substituted into the Zr site in the Laves-phase compound ZrFe 2 , using the perturbed angular correlation of ␥ rays emitted after the ␤ Ϫ decays of 181 Hf probe nuclei. Although the overall crystal structure is cubic, a weak strongly damped electric-quadrupole interaction is observed, which shows no significant temperature dependence over the investigated temperature range from 290-1300 K. Thus below the magnetic ordering temperature T C of 631͑2͒ K we observe combined magnetic-dipole and electric-quadrupole hyperfine interactions. Two separate magnetic components characterize the magnetic-dipole interactions. For the interaction at the primary site, which is occupied by 70-80% of the probes, the Larmor frequency measured at temperature has a value of L ϭ407(1) Mrad sec Ϫ1 . The secondary site is populated by the remaining 20-30% of the probes, for which the corresponding Larmor frequency has a room temperature value of L ϭ579(3) Mrad sec Ϫ1 . We attribute the primary interaction to the ''perfect-crystal'' probe environment at the Zr site, whereas we ascribe the secondary interaction to the enhancement of the transferred hyperfine field by the presence of Fe antisite defects near the Zr site. At temperatures below but very close to T C , those frequencies cannot be determined for either interaction, because the magnetic-hyperfine and the electricquadrupole frequencies converge to comparable values.