Showing papers by "National University of Cuyo published in 1980"
TL;DR: A low‐cost 8‐bit microcomputer interfaced with a sampling oscilloscope yields a versatile <0.35 ns rise time digital boxcar integrator.
Abstract: We describe a new device to produce ribbons of disordered metals by ultrarapid quenching combining an arc furnace with a rotating cylinder. The characterization of samples of disordered La70 Cu30 and La76Au24 prepared using this method shows good agreement with those obtained by other authors for the same alloys.
21 citations
TL;DR: In this article, the spin-lattice coefficients of Mn 2+ in CdTe and ZnTe have been measured and compared with values obtained for Mn 2 + in MgO and CaO.
15 citations
TL;DR: In this paper, the effective hamiltonians commonly used in solid state physics as well as their corresponding perturbative expansions are discussed, from a single pair of equations, and how to obtain, from such equations, the effective Hamiltonians.
4 citations
TL;DR: In this article, a variational method similar to the one used for the Ising model is applied to the Hamiltonian Z(2) lattice gauge theory in three dimensions, and it is shown that the proposal of a gauge-invariant ground state leads to a transition in the Wilson loop integral from the area to the perimeter behavior.
Abstract: A variational method similar to the one used for the Ising model is applied to the Hamiltonian Z(2) lattice gauge theory in three dimensions. It is shown that the proposal of a gauge-invariant ground state leads to a transition in the Wilson loop integral from the area to the perimeter behavior for a value of the coupling constant close to the symmetry point predicted by self-duality. The discontinuity which appears in the variational parameter gives strong evidence in favor of the first-order nature of the transition in contrast to what occurs for the two-dimensional model.
2 citations
Journal Article•
1 citations
TL;DR: In this article, the authors explore the possibility of magnetic reentrance in intermediate valence compounds using a simplified Anderson-Lattice model and obtain the pressure-temperature magnetic phase diagram, showing that for some value of the microscopic parameters the temperature induced two transitions (non-magnetic to magnetically ordered to paramagnetic).
1 citations
TL;DR: In this paper, the authors show that inaccuracy has no bad consequences and that care is necessary when topological consifera t ions arc of relevance, in particular when topology is of relevance.
Abstract: wi th a con t inuous A ( taking i ts values in the Lic Mgebra G of G). E v e n if, in m a n y c i rcumstances , th is inaccuracy has no bad consequences , g rea te r care is necessary when topological cons idera t ions arc of relevance. To see t h a t t he res t r ic t ion to gauge t r ans fo rma t ions of the form (2) (with co~dinuous A) is real ly an undes i rable l imi ta t ion it suffices to note t h a t every such .(2 can be cont inuous ly de fo rmed to a cons t an t one, w h a t e v e r the x m a y be: -Qt(x) = exp [tA(x)], 0 < t-..<< 1. The s i tua t ion is not too bad when ( i U~. For ins tance , in wr i t ing
01 Jan 1980
TL;DR: In this article, low frequency internal friction measurements in the temperature range 4 K to 300 K have been performed on polycristalline 5 N zirconium samples after deformation by tension at 4 K.
Abstract: Low frequency internal friction measurements in the temperature range 4 K to 300 K have been performed on polycristalline 5 N zirconium samples after deformation by tension at 4 K. The initial internal friction spectrum is characterized by the presence of a small relaxation peak P 1 at 96 K with an activation energy of 0.14 eV followed by an always increasing background with a shoulder at about 140 K. It is found that P 1 disappears upon annealing at 180 K. The peak P 2 at about 135 K is present after room temperature annealing. In order to study its “structure” and to determine its activation energy complementary observations of P 2 were carried out at frequencies of 40 Hz and 30 kHz. Values of 0,35 ± 0,05 eV for the high temperature side and 0,10 + 0,02 eV for the low temperature side were obtained.
01 Jan 1980
TL;DR: In this paper, the internal friction spectrum in an Al 4 wt % Cu alloy has been observed during ageing under different conditions and two peaks are observed during the first heating in samples treated as to form G.P. zones and then aged at room temperature.
Abstract: The internal friction spectrum in an Al 4 wt % Cu alloy has been observed during ageing under different conditions. In addition to the well known Zener and precipitation peaks two “extra” peaks are observed. The first one, peak A, shows up during the first heating in samples treated as to form G.P. zones and then aged at room temperature. Its position is independent of the frequency in the range 1 Hz to 50 Hz and its height increases with the ageing time at room temperature. The second one, peak B, which is observed in solubilized samples (ss) at about 280K only for vibration frequencies between 15 to 50Hz, presents the characteristics of a relaxation process with an apparent activation energy of 0,6 eV and it is amplitude dependent. It is found that a torsional deformation of 7,5% at room temperature increases the internal friction by a factor of seven. It is also observed that the maximum growing rate occurs for T ≃ 350 K while the annealing out of the peak begins at T ≃ 380K. The present results are discussed in terms of the disolution of an intermediate phase (peak A), and depinning of dislocation lines from small copper clusters (peak B).