APPLIED PHYSICS GROUP
Prof. Xun-Li WANG
Chair Professor, Department of Physics
Director, Centre for Neutron Scattering
City University of Hong Kong
Elasto-magnetic Coupling in Ferromagnetic Shape Memory Alloys
Smart materials which provide rapid responses to mechanical and magnetic stimuli hold the promise for future generations of sensors and actuators. Ferromagnetic shape memory alloys (FSMAs) which exhibit such responses can transform a wide spectrum of transducer technologies in diversified fields. Compositional and microstructural design of FSMAs with desired magneto-mechanical responses hinges on having a fundamental understanding of the strong magnetoelastic coupling in this class of materials. We study the nature of magnetoelastic coupling in FSMAs with in situ neutron diffraction experiments.
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In ferromagnetic shape memory alloys, the lattice and magnetic moments are coupled. Deformation proceeds through reorientation of martensitic twins. Unloading leads a plastic deformation, but under a magnetic field, the material would return to its original shape. The key is to understand the nature of the magnetoelastic coupling and the controlling parameters.
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Key publications from our group:
[1] H. H. Wu, A. Pramanick, Y. B. Ke, and X.-L. Wang, “Real-space phase field investigation of evolving magnetic domains and twin structures in a ferromagnetic shape memory alloy,” Journal of Applied Physics, 120, 183904 (2016).
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[2] A. Pramanick, A. A. Aczel, G. Samolyuk, V. Lauter, A. Glavic, H. Ambaye, Z. Gai, J. Ma, A. D. Stoica, G. M. Stocks, X.-L. Wang, S. M. Shapiro, “Direct measurement and theoretical modeling of coupled magnetostructural evolution in a ferromagnetic shape memory alloy,” Physical Review B, 92, 134109 (2015).
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[3] A. Pramanick, X.-L. Wang*, A. D. Stoica, C. Yu, Y. Ren, S. Tang, and Z. Gai, “Kinetics of magnetoelastic twin boundary motion in ferromagnetic shape memory alloys,” Physical Review Letters, 112, 217205 (2014).
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[4] A. Pramanick, K. An, A. D. Stoica, X.-L. Wang, “In situ neutron diffraction study of twin reorientation and pseudoplastic strain in Ni-Mn-Ga single crystals,” Scripta Materialia, 65, 540-543 (2011).
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