by jerky propagation of phase fronts related to the appearance of avalanches. In this paper we describe a full analysis of this avalanche behavior using calorimetric heat flux measurements and acoustic emission measurements. Two different propagation modes, namely smooth front propagation and jerky avalanches, were observed in extremely slow measurements with heating and cooling rates as low as a few 10 Avalanches appear to be more common for heating rates faster than 5 10 -3 K/h whereas smooth front propagation occurs in all calorimetric measurements and (almost) exclusively for slower heating rates. Repeated cooling runs were taken after a waiting time of 1 month (and an intermediate heating run). Correlations between the avalanche sequences of the two cooling runs were found for the strongest avalanche peaks but not for the full sequence of avalanches. The memory effect is hence limited to strong avalanches.3

Heat treatment induced martensitic accommodation and adaptive anisotropy in melt spun Ni55Mn22Ga23 (at. %) ribbons J. Appl. Phys. 112, 103512 (2012) Modulated structure in the martensite phase of Ni1.8Pt0.2MnGa: A neutron diffraction study Appl. Phys. Lett. 101, 171904 (2012) Martensitic and magnetic transformation in Mn50Ni50−xSnx ferromagnetic shape memory alloys J. Appl. Phys. 112, 083902 (2012) Ellipsometry applied to phase transitions and relaxation phenomena in Ni2MnGa ferromagnetic shape memory alloy Appl.

Conduction calorimetry has been used to determine with high precision the latent heat and variation in heat capacity which accompany the first order [Formula: see text] phase transition in perovskites with compositions (Ca(1-x)Sr(x))TiO(3), x = 0.65, 0.68, 0.74 (CST65, CST68, CST74). In CST65 (CST68), the latent heat is dissipated/absorbed over a temperature interval of ∼11 K (∼6 K), which is centred on ∼292 K (∼258 K) during cooling and ∼302 K (∼270 K) during heating. The magnitude of the latent heat diminishes with increasing SrTiO(3) content and was not detected in CST74. Integration of the latent heat and excess heat capacity yields small excess entropies, which are consistent with the structural changes being displacive rather than order-disorder in origin. Resonant ultrasound spectroscopy measurements on the same CST65 sample as used for dielectric and calorimetric measurements through the same temperature intervals have allowed quantitative correlations to be made with the bulk modulus, shear modulus and acoustic dissipation parameter, Q(-1). The dielectric anomaly and changes in Q(-1) can be understood as being linear combinations of the properties of the separate I4/mcm and Pbcm phases in proportion to their volume fractions across the two-phase field. A change of only ∼0.5-1 GPa has been detected in the bulk modulus but the shear modulus softens by ∼5-8 GPa as the transition interval is approached from above and below. This shear mode softening presumably reflects clustering and/or phonon softening in both the I4/mcm and Pbcm structures. This pattern of structure-property relations could be typical of first order transitions in perovskites where there is no group/subgroup relationship between the high and low symmetry phases.

A conduction calorimetry technique has been used to characterize qualitatively and quantitatively first-order phase transitions. A series of long-period square thermal pulses superimposed on a temperature ramp (square-modulated differential thermal analysis) is applied to the sample and the heat flux is measured by highly sensitive fluxmeters. In a single run, the specific heat behavior is determined and the heat flux due to the temperature dependence of the specific heat is obtained. This contribution is subtracted from the measured heat flux and the value of the latent heat is extracted. The analysis of the fluxmeter’s response allows us to know if it is necessary to carry out a second experiment in order to study the kinetics of the transformation in depth. In this second run, the temperature ramp is only used to obtain the DTA trace. Four materials with first-order phase transitions, ranging from narrow coexistence intervals to very large ones and exhibiting smooth or very abrupt transformations, have been studied using this technique.

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