Scaling of Average Avalanche Shapes for Acoustic Emission during Jerky Motion of Single Twin Boundary in Single-Crystalline Ni(2)MnGa

Temporal average shapes of crackling noise avalanches, [Formula: see text] ([Formula: see text] is the detected parameter proportional to the interface velocity), have self-similar behavior, and it is expected that by appropriate normalization, they can be scaled together according to a universal scaling function. There are also universal scaling relations between the avalanche parameters (amplitude, [Formula: see text] , energy, [Formula: see text] , size (area), [Formula: see text] and duration, [Formula: see text]), which in the mean field theory (MFT) have the form [Formula: see text] , [Formula: see text] , [Formula: see text]. Recently, it turned out that normalizing the theoretically predicted average [Formula: see text] function at a fixed size, [Formula: see text] ([Formula: see text] and [Formula: see text] are non-universal, material-dependent constants) by [Formula: see text] and the rising time, [Formula: see text] , a universal function can be obtained for acoustic emission (AE) avalanches emitted during interface motions in martensitic transformations, using the relation [Formula: see text] too, where [Formula: see text] is a mechanism-dependent constant. It was shown that [Formula: see text] also appears in the scaling relations [Formula: see text] and [Formula: see text] , in accordance with the enigma for AE, that the above exponents are close to 2 and 1, respectively (in the MFT limit, i.e., with [Formula: see text] 0, they are 3 and 2, respectively). In this paper, we analyze these properties for acoustic emission measurements carried out during the jerky motion of a single twin boundary in a Ni(50)Mn(28.5)Ga(21.5) single crystal during slow compression. We show that calculating from the above-mentioned relations and normalizing the time axis of the average avalanche shapes with [Formula: see text] , and the voltage axis with [Formula: see text] , the averaged avalanche shapes for the fixed area are well scaled together for different size ranges. These have similar universal shapes as those obtained for the intermittent motion of austenite/martensite interfaces in two different shape memory alloys. The averaged shapes for a fixed duration, although they could be acceptably scaled together, showed a strong positive asymmetry (the avalanches decelerate much slower than they accelerate) and thus did not show a shape reminiscent of an inverted parabola, predicted by the MFT. For comparison, the above scaling exponents were also calculated from simultaneously measured magnetic emission data. It was obtained that the [Formula: see text] values are in accordance with theoretical predictions going beyond the MFT, but the AE results for φ are characteristically different from these, supporting that the well-known enigma for AE is related to this deviation.