438 research outputs found
Magnetic characterization of the frustrated three-leg ladder compound [(CuCl2tachH)3Cl]Cl2
We report the magnetic features of a new one-dimensional stack of
antiferromagnetically coupled equilateral copper(II) triangles. High-field
magnetization measurements show that the interaction between the copper
triangles is of the same order of magnitude as the intra-triangle exchange
although only coupled via hydrogen bonds. The infinite chain turns out to be an
interesting example of a frustrated cylindrical three-leg ladder with competing
intra- and inter-triangle interactions. We demonstrate that the ground state is
a spin singlet which is gaped from the triplet excitation.Comment: 6 pages, 9 figures, revised version submitted to Phys. Rev. B. More
information at http://obelix.physik.uni-osnabrueck.de/~schnack
Statistical Transfer Matrix Study of the Multileg Ising Ladders and Tubes
Finite temperature properties of symmetric multileg Ising ladders and
tubes are investigated using the statistical transfer matrix method. The
temperature dependences of the specific heat and entropy are calculated. In the
case of tubes, it is found that the ground state entropy shows an even-odd
oscillation with respect to the number of legs. The same type of oscillation is
also found in the ground state energy. On the contrary, these oscillations do
not take place in ladders. From the temperature-dependence of the specific
heat, it is found that the lowest excitation energy is 4J for even-leg ladders
while it is 2J otherwise, The physical origin of these behaviors is discussed
based on the structure of excitations.Comment: 6 pages, 9 figure
A unitary correlation operator method
The short range repulsion between nucleons is treated by a unitary
correlation operator which shifts the nucleons away from each other whenever
their uncorrelated positions are within the replusive core. By formulating the
correlation as a transformation of the relative distance between particle
pairs, general analytic expressions for the correlated wave functions and
correlated operators are given. The decomposition of correlated operators into
irreducible n-body operators is discussed. The one- and two-body-irreducible
parts are worked out explicitly and the contribution of three-body correlations
is estimated to check convergence. Ground state energies of nuclei up to mass
number A=48 are calculated with a spin-isospin-dependent potential and single
Slater determinants as uncorrelated states. They show that the deduced energy-
and mass-number-independent correlated two-body Hamiltonian reproduces all
"exact" many-body calculations surprisingly well.Comment: 43 pages, several postscript figures, uses 'epsfig.cls'. Submitted to
Nucl. Phys. A. More information available at http://www.gsi.de/~fm
El híbrido "Glandularia laciniata" x "G. peruviana" y su anfidiploide artificial
En el trabajo presente se informan las observaciones morfológicas y citogenéticas realizadas en las especies Glandularia laciniata (L.) Schnack et Covas, G. peruviana (L.) Small, en su híbrido diploide y en el correspondiente alotetraploide, obtenido por tratamiento con colchicina. El objeto fué determinar el grado relativo de parentesco entre las especies progenitoras. Se llega a la conclusión de que el tetraploide en estudio es un alopoliploide segmentario y que las especies progenitoras tienen un grado relativamente bajo (aunque no muy bajo) de parentesco.Facultad de Ciencias Agrarias y Forestale
Magneto- and barocaloric properties of the ferro-antiferromagnetic sawtooth chain
Materials that are susceptible to pressure and external magnetic fields allow
the combined use of both for caloric processes. Here we report investigations
of the ferromagnetic-antiferromagnetic sawtooth chain that due to its critical
behavior not only allows for both barocaloric as well as magnetocaloric
processes but also features very large cooling rates in the vicinity of the
quantum critical point.Comment: 6 pages, 7 figure
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