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Heusler alloys are suitable materials for sensors and actuators [1]. The current challenge in the utilization of shape memory Heusler alloys remains in their downsizing [2]. In this work we present such materials in the form of thin films and nanowires, which were fabricated using electrodeposition. This approach presents a scalable method for fabrication of shape memory materials, which can be used for sensing and actuation in the nanoscale.
Electrodeposition of Ni$_2$FeGa thin films and nanowires, which show a shape memory behavior due to a martensitic transformation capability, was followed by a complete substitution of the Ga atom in their composition by Tl. The Ga substitution resulted in off-stoichiometric Ni-Fe-Tl nanowires with a phase transition at the temperature of $\approx$ 350 K, confirmed by structural and magnetic analysis.
First-order reversal curve analysis of an array of the Ni-Fe-Tl nanowires reveals a change in their magnetization process before and after the phase transition, enabling contactless sensing mechanism of the nanowires’ magnetostructural response [3,4]. Moreover, the phase transition-driven magnetization variations make the nanowires suitable for hyperthermic application. Wide temperature hysteresis of the nanowires’ phase transition offers a possibility to gradually heat the nanowires under an alternating magnetic field. The heating process can be automatically interrupted after the nanowires transform into the high-temperature phase due to a > 70$\%$ change in the hysteresis losses between the magnetically soft austenite and magnetically hard martensitic phase.
Acknowledgements
The authors would like to thank the following projects for the financial support of the presented research: The projects APVV-16-0079 and APVV-20-0205 of the Slovak Research and Development Agency, and projects VEGA 1/0053/19, VEGA 1/0180/23, as well as the project VVGS-2022-2408 of the UPJS.
References
[1] L. Frolova et al., “Smart Shape Memory Actuator Based on Monocrystalline Ni2FeGa Glass-Coated Microwire,” IEEE Trans Magn, vol. 54, no. 11, pp. 1–5, Nov. 2018, doi: 10.1109/TMAG.2018.2848670.
[2] M. Varga et al., “FORC and TFORC analysis of electrodeposited magnetic shape memory nanowires array,” J Alloys Compd, vol. 897, p. 163211, Mar. 2022, doi: 10.1016/j.jallcom.2021.163211.
[3] C. I. Dobrotǎ and A. Stancu, “What does a first-order reversal curve diagram really mean? A study case: Array of ferromagnetic nanowires,” J Appl Phys, vol. 113, no. 4, p. 043928, Jan. 2013, doi: 10.1063/1.4789613.
[4] M. R. Zamani Kouhpanji, A. Ghoreyshi, P. B. Visscher, and B. J. H. Stadler, “Facile decoding of quantitative signatures from magnetic nanowire arrays,” Sci Rep, vol. 10, no. 1, p. 15482, Sep. 2020, doi: 10.1038/s41598-020-72094-4.
