eduard vives

The elastocaloric effect in the vicinity of the martensitic transition of a Cu-Zn-Al has been studied by inducing the transition by strain or stress measurements. While transition trajectories show significant differences, the entropy change associated with the whole transformation (\DeltaSt) is coincident in both kind of experiments since entropy production is small compared to \DeltaSt. The values agree with estimations based on the Clausius- Clapeyron equation. The possibility of using these materials for mechanical refrigeration is also discussed.

The behaviour of the Random Anisotropy Ising model at T=0 under local relaxation dynamics is studied. The model includes a dominant ferromagnetic interaction and assumes an infinite anisotropy at each site along local anisotropy axes which are randomly aligned. Two different random distributions of anisotropy axes have been studied. Both are characterized by a parameter that allows control of the degree of disorder in the system. By using numerical simulations we analyze the hysteresis loop properties and characterize the statistical distribution of avalanches occuring during the metastable evolution of the system driven by an external field. A disorder-induced critical point is found in which the hysteresis loop changes from displaying a typical ferromagnetic magnetization jump to a rather smooth loop exhibiting only tiny avalanches. The critical point is characterized by a set of critical exponents, which are consistent with the universal values proposed from the study of other simpler models.

An experimental study of acoustic emission (AE) in a single crystal and in a polycrystalline sample of Fe 68.8 Pd 31.2 is presented. The samples are studied in a temperature range that is known to include not only a martensitic transition (MT) but also premartensitic ...

We present an alternative formulation of Equilibrium Statistical Mechanics which follows the method based on the maximum statistical entropy principle in Information Theory combined with the use of Massieu–Planck functions. The different statistical ensembles are obtained by a suitable restriction of the whole set of available microstates. The main advantage is that all of the equations that relate the average values with derivatives of the partition function are formally identical in the different ensembles. Moreover, Einstein's fluctuation formula is also derived within the same framework. This provides a suitable starting point for the calculation of fluctuations of extensive and intensive variables in any statistical ensemble.

An experimental study of acoustic emission (AE) in a single crystal and in a polycrystalline sample of Fe 68.8 Pd 31.2 is presented. The samples are studied in a temperature range that is known to include not only a martensitic transition (MT) but also premartensitic ...