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 ±J\pm J Multileg Ising Ladders and Tubes

Finite temperature properties of symmetric $\pm J$ 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