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We have revealed an unprecedented shear anisotropy in Ni–Mn–Ga, the most studied multiferroic magnetic shape memory alloy. Its extreme directional dependence of mechanical properties—the “slipping” of atomic planes—is comparable to the softness of graphite and other van der Waals materials. This observation provides new insight into the mechanism behind the supermobility of twin boundaries, which enables the magnetic shape memory effect, and guides the search for new functional materials.
Description
Visualisation of extremely strong elastic anisotropy in five-layered modulated Ni–Mn–Ga martensite.(a) 3D plots of slowness (1/phase velocity) for the softest TA₂ phonon reveal a pronounced elastic instability.(b) 3D map of Young’s modulus illustrating the extreme directional dependence of stiffness.