Kosogor Anna, Soprunyuk Viktor, Koraltan Sabri, Golub Vladimir, Velyhotskyi Dmytro, Chernenko Volodymyr, Hosoda Hideki, Suess Dieter, Schranz Wilfried, L'vov Victor A
Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090, Vienna, Austria.
Institute of Magnetism NASU and MESU, Kyiv, 03142, Ukraine.
Sci Rep. 2024 May 28;14(1):12199. doi: 10.1038/s41598-024-62909-z.
The magnetization value and electric resistivity of the single-crystalline sample of NiFeCoGa shape memory alloy were measured. The elastic modulus was determined by the Dynamic Mechanical Analysis (DMA). The characteristic temperatures of martensitic transformation (MT) of the alloy were estimated from the temperature dependences of magnetization, electric resistivity and elastic modulus. A significant disparity between MT temperatures resulting from DMA and those estimated from magnetic and resistivity measurements was discovered. It was argued that the discrepancy is caused by the non-uniform mechanical stressing of twinned single crystal by the DMA analyzer. Moreover, the DMA measurements revealed a significant decrease of the elastic modulus of twinned martensite under the applied magnetic field of 1.5 kOe. To explain this effect, the temperature-dependent Young's modulus of twinned crystal lattice was computed. The computations showed that the experimentally observed field-induced change of the elastic modulus is caused by the stress-assisted detwinning of the crystal lattice by the applied magnetic field.
对NiFeCoGa形状记忆合金单晶样品的磁化值和电阻率进行了测量。通过动态力学分析（DMA）测定了弹性模量。根据磁化强度、电阻率和弹性模量的温度依赖性估算了合金马氏体相变（MT）的特征温度。发现DMA得出的MT温度与通过磁性和电阻率测量估算出的MT温度之间存在显著差异。有人认为，这种差异是由DMA分析仪对孪晶单晶施加的不均匀机械应力造成的。此外，DMA测量结果表明，在1.5 kOe的外加磁场下，孪晶马氏体的弹性模量显著降低。为了解释这种效应，计算了孪晶晶格的温度依赖性杨氏模量。计算结果表明，实验观察到的弹性模量的场致变化是由外加磁场对晶格的应力辅助去孪晶作用引起的。
