Direct Observations of Mechanical Strain-Induced Wavevector Switching in a (Fe,Ni,Pd)₃P Magnet with Anisotropic...

A strain-induced phase transition is one of the noteworthy phenomena in materials science and condensed matter physics. Electrical and optical switching via strain-induced phase transitions at room temperature is applicable to straintronics, which is an emerging field focusing on low-energy operation of next-generation computing and memory devices. While strain-induced structural and magnetic transitions have been extensively investigated, real-space observation of these phase transitions is still a considerable challenge. In this study, we investigated magnetic textures under uniaxial compressive strain by using Lorentz transmission electron microscopy (L-TEM) for a (Fe_0.63Ni_0.3Pd_0.07)₃P magnet with S₄ symmetry, and hence with anisotropic Dzyaloshinskii-Moriya interaction. L-TEM observations, in conjunction with the in situ nanoindentation technique, demonstrated a switching of the wavevector (q) of magnetic stripe domains when the strain direction is along the stripes, while the q direction does not change when the strain is applied perpendicularly to the stripes. These observations are in accordance with those predicted in micromagnetic simulations. Moreover, calculations using the finite element method reveal that spatially concentrated compressive stress triggers the switching of magnetic stripes. These results provide a possibility to control magnetic textures by the application of strain in electronic materials.