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25 May 2004 Low-frequency conductance fluctuations in a shape memory alloy near the martensite transition
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Proceedings Volume 5469, Fluctuations and Noise in Materials; (2004)
Event: Second International Symposium on Fluctuations and Noise, 2004, Maspalomas, Gran Canaria Island, Spain
We have investigated the conductance fluctuation in a shape memory alloy (NiTi-Nitinol) near its martensite transition in order to study how the noise evolves near a phase transition that is driven by long range elastic interactions. The alloy has a martensite start and completion temperatures of 333 K and 325 K respectively and change of around 6%-8% in resistance at the transition. The conductance fluctuation (noise) measurements were carried out using a 5-probe ac technique in the temperature interval 200 K to 400 K in wire samples with typical thickness 5 μm and width of 120 μm. The samples were annealed at high temperature to remove any effect of previous temperature or strain cycle. We made the following observations: (1) There is a large change in the measured noise spectral power S(f) at the transition. (2) Away from transition temperature S(f) follows a 1/f-type behavior. This changes drastically near the transition, where large spectral density appears for f <1 Hz, and this strong dependence tends to saturate around 1 mHz. (3) Close to the transition, the probability density function (PDF) deviates from a Gaussian distribution, and shows a significant contribution from a power-law distribution. (4) When the transition is tuned by an applied constant stress (staying close to but below the transition temperature range), a similar strongly frequency-dependent low frequency S(f) appears, accompanied by a non-Gaussian PDF with a power-law statistics.
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Arindam Ghosh, Ayan Guha, and Arup Kumar Raychaudhuri "Low-frequency conductance fluctuations in a shape memory alloy near the martensite transition", Proc. SPIE 5469, Fluctuations and Noise in Materials, (25 May 2004);

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