Towards the determination of elastic constants on a submicron scale using scanning acoustic force microscopy
Proceedings of the IEEE Ultrasonics Symposium 1 (1997) 549-552
Abstract:
This paper reports first steps towards the determination of elastic constants with submicron lateral resolution. The experimental phase velocity dispersion data were obtained on a micron scale using scanning acoustic force microscopy. The minimum of the corresponding error field is only weakly localized, thus giving a large error for the elastic constants. The localization can not be increased by using more of data points. In order to decrease the elastic constant's error, a Love mode is additionally regarded. However, the error field crossing is in this case not leading to a significant increase of the accuracy. We propose the inclusion of further surface guided modes.Discovery of a second family of bismuth-oxide-based superconductors
Nature 390:6656 (1997) 148-149
Abstract:
The superconducting oxide BaPb(1-x)Bi(x)O3, discovered in 1975 (ref. 1), is an exotic system having an unusually high transition temperature (T(c)) of ~12K, despite a relatively low density of states at the Fermi level. The subsequent prediction that doping the electronically inactive barium donor sites, instead of the bismuth sites, might induce superconductivity with a higher T(c) led to the discovery in 1988 of superconductivity in the Ba(1-x)K(x)BiO3 system (T(c) ~30 K for x = 0.4). But it remains an open question why many of the superconducting properties of these materials are similar to those of the well-known copper oxide superconductors, despite their pronounced structural differences: the former have a three-dimensional bismuth-oxygen framework, whereas the structures of the latter are predominantly two-dimensional, consisting of copper-oxygen planes. Understanding of the copper oxide superconductors has gained immensely from the study of many different superconducting systems, and so it might be expected that the identification of bismuth oxide superconductors beyond the substituted BaBiO3 compounds will prove to be similarly fruitful. Here we report the synthesis of a second family of superconducting bismuth oxides, based on SrBiO3. We show that partial substitution of potassium or rubidium for strontium induces superconductivity with: T(c) values of ~12 K for Sr(1-x)K(x)BiO3 (x= 0.45-0.6) and ~13K for Sr(1-x)Rb(x)BiO3 (x = 0.5).Hysteresis of the Pressure-Induced Jahn-Teller Switch in Deuterated Ammonium Copper(II) Tutton Salt, (ND(4))(2)[Cu(D(2)O)(6)](SO(4))(2).
Inorg Chem 36:15 (1997) 3382-3385
Pressure-induced orthorhombic-rhombohedral phase transition in NdNiO3
Physica B: Condensed Matter 234-236 (1997) 15-17
Abstract:
We report the first experimental observation of a pressure-induced structural phase transition in the RNiO3 series. At ≈ 40 kbar, the space group of NdNiO3 changes from Pbnm (orthorhombic) to the more symmetrical R3̄c (rhombohedral). This experiment confirms our previous results on PrNiO3 indicating that the symmetry of the structure increases with pressure.Multiple defects in overdoped Tl2 Ba2 CuO6+δ : Effects on structure and superconductivity
Physica C: Superconductivity and its Applications 277:3-4 (1997) 170-182