Statistical Analysis of Jerky Character of DSC Signals Obtained From the Martensitic Transformation in Single Crystalline Ni2MnGa

The jerky character of austenite/martensite phase transformation in Ni₂MnGa single crystal has been investigated by thermal cycling using Differential Scanning Calorimeter (DSC) at very low cooling rate (0.1 K/min). The obtained curves show several split peaks (jerky steps) related to the formation and growth of the martensitic nuclei. The statistical analysis of the obtained DSC signals was carried out similarly as it was done e.g. in [1, 2]. The amplitude A and energy E distribution functions clearly showed power-law like nature, without exponential cut-off and ambiguous behavior on the low-amplitude/energy side. These distortions caused by the limitation of the measuring device and the background noise. To achieve a fine signal, this noise had to be filtered with properly chosen threshold. The exponents characterizing the probability distributions (a and e respectively) have been obtained by maximum-likelihood fitting methods. The analysis indicated, that both the amplitude and energy exponents were independent of the number of thermal cycles and have the following values a= 1.4(0.12) as well as e=1.2(0.07), satisfying the scaling relation [3] e @[(a -1)/z +1] [3,4] (E~A^z, with z=2).

[1] E. Vives et al, Phys. Rev. B 80, 180101(R) (2009).

[2] M. C. Gallardo et.al. Phys.Rev. B 81, 174102 (2010).

[3] E. Vives et al. Phys. Rev. B 52, 12644 (1995).

[4] A. Planes et al. J. of Alloys and Comp. (2012) in print