Hysteresis in the de Haas-van Alphen effect

A hysteresis loop is observed for the first time in the de Haas-van Alphen (dHvA) effect of beryllium at low temperatures and quantizing magnetic field applied parallel to the hexagonal axis of the single crystal. The irreversible behavior of the magnetization occurs at the paramagnetic part of the dHvA period in conditions of Condon domain formation arising by strong enough dHvA amplitude. The resulting extremely nonlinear response to a very small modulation field offers the possibility to find in a simple way the Condon domain phase diagram. From a harmonic analysis, the shape and size of the hysteresis loop is constructed.     

Magnetoresistance anisotropy in Si /SiGe in tilted magnetic fields: experimental evidence for a stripe-phase formation

We observe pronounced transport anisotropies in magnetotransport experiments performed in the two-dimensional electron system of a Si/SiGe heterostructure. They occur when an in-plane field is used to tune two Landau levels with opposite spin to energetic coincidence. The observed anisotropies disappear drastically for temperatures above 1 K. We propose that our experimental findings may be caused by the formation of a unidirectional stripe phase oriented perpendicular to the in-plane field.     

Oscillatory melting temperature of the vortex smectic phase in layered superconductors

We report on transport measurements of YBa 2Cu 3O (7-delta) single crystals with different oxygen contents in the geometry B, J ||ab (J perpendicularB). Our data show that the vortices become confined between the Cu-O planes below a well-defined temperature at which the effective size 2xi of the vortex core is approximately equal to the period of the Cu-O layers. This confinement strongly increases the vortex liquid freezing temperature. A new melting line is found separating a vortex liquid and a smectic phase, which shows an oscillatory field dependence reflecting differences between commensurate and incommensurate smectic states.     

Turbulent cascade modeling of single and bubbly two-phase turbulent flows

The analysis of turbulent two-phase flows requires closure models in order to perform reliable computational multiphase fluid dynamics (CMFD) analyses. A spectral turbulence cascade-transport model, which tracks the evolution of the turbulent kinetic energy from large to small liquid eddies, has been developed for the analysis of the homogeneous decay of isotropic single and bubbly two-phase turbulence. This model has been validated for the decay of homogeneous, isotropic single and two-phase bubbly flow turbulence for data having a 5 mm mean bubble diameter. The Reynolds number of the data based on bubble diameter and relative velocity is approximately 1400.     

Ruthenium(IV) pyrochlore oxides: Realization of novel electronic properties through substitution at A- and B-sites

We describe an exploratory investigation of the structure and electronic properties of new ruthenium(IV) pyrochlore oxides and their manganese-substituted derivatives. Our investigations have revealed several, hitherto unreported, electronic ground states for these materials: a metallic and Pauli paramagnetic state for BiPbRu₂O_6.5 that turns into a semiconducting ferromagnetic spin-glass state at 50 K for BiPbRuMnO_6.5; a metallic state that likely shows a charge density wave (CDW) instability at 50–225 K for Bi_1.50Zn_0.50Ru₂O_6.75 that is suppressed by manganese substitution in Bi_1.50Zn_0.50Ru_1.75Mn_0.25O_6.50; and a metallic ferromagnetic spin-glass like state for Pb₂Ru_1.75Mn_0.25O_6.15. The results indeed affirm the richness of the electronic properties of ruthenium-based metal oxides.     

BaAuP and BaAuAs,Synthesis via Disproportionation of Gold upon Interaction with Pnictides as Bases

Gold disproportinates in the presence of the Zintl phases Ba₃P₂ or Ba₃As₂ forming BaAuP and BaAuAs, respectively, and BaAu₂. The air and moisture sensitive ternary compounds crystallise in the ZrBeSi type of structure, an ordered variant of AlB₂: BaAuP (P6₃/mmc; a = 440.68(6) pm; c = 899.8(2) pm; R₁ = 0.0237; 183 independent reflections); BaAuAs (P6₃/mmc; a = 453.53(5) pm; c = 902.7(1) pm; R₁ = 0.0255; 168 independent reflections). Both compounds, which are accessible as pure phases by reacting BaP or BaAs with gold, can be classified as poor metallic conductors.