An integrated study of earth resources in the State of California based on ERTS-1 and supporting aircraft data, volume 1

There are no author-identified significant results in this report

An integrated study of earth resources in the State of California based on ERTS-1 and supporting aircraft data

There are no author-identified significant results in this report

An integrated study of earth resources in the state of California using remote sensing techniques

The University of California has been conducting an investigation which seeks to determine the usefulness of modern remote sensing techniques for studying various components of California's earth resources complex. Most of the work has concentrated on California's water resources, but with some attention being given to other earth resources as well and to the interplay between them and California's water resources

Clustered States as a New Paradigm of Condensed Matter Physics

We argue that several materials of much current interest in condensed matter physics share common phenomenological aspects that only very recent investigations are unveiling. The list includes colossal magnetoresistance manganites, high temperature superconducting cuprates, diluted magnetic semiconductors, and others. The common aspect is the relevance of intrinsic inhomogeneities in the form of "clustered states", as explained in the text.Comment: elsart3, 6 pages, 5 figures. Invited paper for the Conference Proceedings of the International Conference on Magnetism, Rome, July 200

Local Ferromagnetism in Microporous Carbon with the Structural Regularity of Zeolite Y

Magnetization M(H,T) measurements have been performed on microporous carbon (MC) with a three-dimensional nano-array structure corresponding to that of a zeolite Y supercage. The obtained results unambiguously demonstrate the occurrence of high-temperature ferromagnetism in MC, probably originating from a topological disorder associated with curved graphene sheets. The results provide evidence that the ferromagnetic behavior of MC is governed by isolated clusters in a broad temperature range, and suggest the occurrence of percolative-type transition with the temperature lowering. A comparative analysis of the results obtained on MC and related materials is given.Comment: To be published in Physical Review B (2003

Perturbative calculation of the spin-wave dispersion in a disordered double-exchange model

We study the spin-wave dispersion of localized spins in a disordered double-exchange model using the perturbation theory with respect to the strength of the disorder potential. We calculate the dispersion upto the next-leading order, and extensively examine the case of one-dimension. We show that in that case, disorder yields anomalous gapped-like behavior at the Fermi wavenumber of the conduction electrons.Comment: 9 pages, 5 figure

Colossal magnetocapacitance and scale-invariant dielectric response in phase-separated manganites

Thin films of strongly-correlated electron materials (SCEM) are often grown epitaxially on planar substrates and typically have anisotropic properties that are usually not captured by edge-mounted four-terminal electrical measurements, which are primarily sensitive to in-plane conduction paths. Accordingly, the correlated interactions in the out-of-plane (perpendicular) direction cannot be measured but only inferred. We address this shortcoming and show here an experimental technique in which the SCEM under study, in our case a 600 Angstrom-thick (La1-yPry)0.67Ca0.33MnO3 (LPCMO) film, serves as the base electrode in a metal-insulator-metal (MIM) trilayer capacitor structure. This unconventional arrangement allows for simultaneous determination of colossal magnetoresistance (CMR) associated with dc transport parallel to the film substrate and colossal magnetocapacitance (CMC) associated with ac transport in the perpendicular direction. We distinguish two distinct strain-related direction-dependent insulator-metal (IM) transitions and use Cole-Cole plots to establish a heretofore unobserved collapse of the dielectric response onto a universal scale-invariant power-law dependence over a large range of frequency, temperature and magnetic field.Comment: 32 pages, 4 figures, Supplementary section included, Submitted to Nature Physic

Single-Band Model for Diluted Magnetic Semiconductors: Dynamical and Transport Properties and Relevance of Clustered States

Dynamical and transport properties of a simple single-band spin-fermion lattice model for (III,Mn)V diluted magnetic semiconductors (DMS) is here discussed using Monte Carlo simulations. This effort is a continuation of previous work (G. Alvarez, Phys. Rev. Lett. 89, 277202 (2002)) where the static properties of the model were studied. The present results support the view that the relevant regime of J/t (standard notation) is that of intermediate coupling, where carriers are only partially trapped near Mn spins, and locally ordered regions (clusters) are present above the Curie temperature T_C. This conclusion is based on the calculation of the resistivity vs. temperature, that shows a soft metal to insulator transition near T_C, as well on the analysis of the density-of-states and optical conductivity. In addition, in the clustered regime a large magnetoresistance is observed in simulations. Formal analogies between DMS and manganites are also discussed.Comment: Revtex4, 20 figures. References updated, minor changes to figures and tex

Proximity induced metal/insulator transition in YBa2Cu3O7/La2/3Ca1/3MnO3Y Ba_2 Cu_3 O_7 / La_{2/3} Ca_{1/3} Mn O_3 superlattices

The far-infrared dielectric response of superlattices (SL) composed of superconducting YBa$_{2}$Cu$_{3}$O$_{7}$ (YBCO) and ferromagnetic La$_{0.67}$% Ca$_{0.33}$MnO$_{3}$ (LCMO) has been investigated by ellipsometry. A drastic decrease of the free carrier response is observed which involves an unusually large length scale of d$^{crit}\approx$20 nm in YBCO and d$^{crit}\approx$10 nm in LCMO. A corresponding suppression of metallicity is not observed in SLs where LCMO is replaced by the paramagnetic metal LaNiO$_{3}$. Our data suggest that either a long range charge transfer from the YBCO to the LCMO layers or alternatively a strong coupling of the charge carriers to the different and competitive kind of magnetic correlations in the LCMO and YBCO layers are at the heart of the observed metal/insulator transition. The low free carrier response observed in the far-infrared dielectric response of the magnetic superconductor RuSr$_{2}$GdCu$_{2}$O$_{8}$ is possibly related to this effect

Glass Transition in the Polaron Dynamics of CMR Manganites

Neutron scattering measurements on a bilayer manganite near optimal doping show that the short-range polarons correlations are completely dynamic at high T, but then freeze upon cooling to a temperature T* 310 K. This glass transition suggests that the paramagnetic/insulating state arises from an inherent orbital frustration that inhibits the formation of a long range orbital- and charge-ordered state. Upon further cooling into the ferromagnetic-metallic state (Tc=114 K), where the polarons melt, the diffuse scattering quickly develops into a propagating, transverse optic phonon.Comment: 4 pages, 4 figures. Physical Review Letters (in Press