19,267 research outputs found
Possibilidades de produção de frutos de açaizeiros em área de terra firme no Estado do Pará.
Publicado também: FRAZÃO, D. A. C.; HOMMA, A. K. O; VIÉGAS, I. de J. M. (Ed.). Contribuição ao desenvolvimento da fruticultura na Amazônia. Belém, PA: Embrapa Amazônia Oriental, 2006. p. 91-97
A model for the phase separation controlled by doping and the internal chemical pressure in different cuprate superconductors
In the framework of a two-band model, we study the phase separation regime of
different kinds of strongly correlated charge carriers as a function of the
energy splitting between the two sets of bands. The narrow (wide) band
simulates the more localized (more delocalized) type of charge carriers. By
assuming that the internal chemical pressure on the CuO layer due to
interlayer mismatch controls the energy splitting between the two sets of
states, the theoretical predictions are able to reproduce the regime of phase
separation at doping higher than 1/8 in the experimental pressure-doping-
phase diagram of cuprates at large microstrain as it appears in overoxygenated
LaCuO.Comment: 8 pages, 5 figures, submitted to Phys. Rev.
Low-temperature ordered phases of the spin- XXZ chain system CsCoCl
In this study the magnetic order of the spin-1/2 XXZ chain system
CsCoCl in a temperature range from 50 mK to 0.5 K and in applied
magnetic fields up to 3.5 T is investigated by high-resolution measurements of
the thermal expansion and the specific heat. Applying magnetic fields along a
or c suppresses completely at about 2.1 T. In addition, we find
an adjacent intermediate phase before the magnetization saturates close to 2.5
T. For magnetic fields applied along b, a surprisingly rich phase diagram
arises. Two additional transitions are observed at critical fields T and T, which we propose to
arise from a two-stage spin-flop transition.Comment: 10 pages, 10 figure
Ferromagnetic coupling and magnetic anisotropy in molecular Ni(II) squares
We investigated the magnetic properties of two isostructural Ni(II) metal
complexes [Ni4Lb8] and [Ni4Lc8]. In each molecule the four Ni(II) centers form
almost perfect regular squares. Magnetic coupling and anisotropy of single
crystals were examined by magnetization measurements and in particular by
high-field torque magnetometry at low temperatures. The data were analyzed in
terms of an effective spin Hamiltonian appropriate for Ni(II) centers. For both
compounds, we found a weak intramolecular ferromagnetic coupling of the four
Ni(II) spins and sizable single-ion anisotropies of the easy-axis type. The
coupling strengths are roughly identical for both compounds, whereas the
zero-field-splitting parameters are significantly different. Possible reasons
for this observation are discussed.Comment: 7 pages, 7 figure
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