Competing `soft' dielectric phases and detailed balance in thin film manganites

Using frequency dependent complex capacitance measurements on thin films of the mixed-valence manganite (La$_{1-y}$Pr$_{y}$)$_{1-x}$Ca$_{x}$MnO$_{3}$, we identify and resolve the individual dielectric responses of two competing dielectric phases. We characterize their competition over a large temperature range, revealing they are in dynamic competition both spatially and temporally. The phase competition is shown to be governed by the thermodynamic constraints imposed by detailed balance. The consequences of the detailed balance model strongly support the notion of an `electronically soft' material in which continuous conversions between dielectric phases with comparable free energies occur on time scales that are long compared with electron-phonon scattering times.Comment: 8 pages, 7 figure

Vortex configurations and dynamics in elliptical pinning sites for high matching fields

Using numerical simulations we study the configurations, dynamics, and melting properties of vortex lattices interacting with elliptical pinning sites at integer matching fields with as many as 27 vortices per pin. Our pinning model is based on a recently produced experimental system [G. Karapetrov et al., Phys. Rev. Lett. 95, 167002 (2005)], and the vortex configurations we obtain match well with experimental vortex images from the same system. We find that the strong pinning sites capture more than one vortex each, and that the saturation number of vortices residing in a pin increases with applied field due to the pressure from the surrounding vortices. At high matching fields, the vortices in the intestitial regions form a disordered triangular lattice. We measure the depinning thresholds for both the x and y directions, and find distinctive dynamical responses along with highly anisotropic thresholds. For melting of the vortex configurations under zero applied current, we find multi-step melting transitions in which the interstitial vortices melt at a much lower temperature than the pinned vortices. We associate this with signatures in the specific heat.Comment: 11 pages, 13 postscript figure

Optical information storage

An optical disc including a medium having both a continuous phase and a non-continuous phase yields excellent contrast and stability for optical recording purposes. Exemplary of materials that form the desired multi-phase system are those produced by sputtering metals such as indium in an oxygen environment.Published versio

Oceanographic features in the lee of the windward and leeward islands: ERTS and ship data

Analysis of the ERTS data in portions of the eastern Caribbean are presented for October 1972 showing features which are, as yet, not explained. Ground truth data obtained in that area during November 1972 are presented. These include vertical temperature structure in the mixed layer and thermocline, and surface measurements of salinity, temperature, and chlorophyll

Unambiguous determination of the g-factor for holes in bismuth at high B/T

Magnetotransport has been investigated in high purity bismuth crystals in static magnetic fields as high as 20 T and temperatures as low as 25 mK. This high B/T ratio permits observation of pronounced Shubnikov-de Haas oscillations over a wide field range and up to fields where most of the carriers are in the lowest Landau level. For transport currents in the bisectrix or binary directions and field in the perpendicular trigonal direction, we have observed doublet splittings centered on each Shubnikov-de Haas oscillation. These splittings exhibit a quadratic dependence on field and disappear before the last oscillation. Our observations allow us to conclude unambiguously that already when the Landau level index is as high as 2 the carriers are fully polarized and that the g-factor for holes with the field in the trigonal direction is 35.3(4).Comment: 4 pages, 3 figure