Coupling of magnetism and plastic deformation in Heusler intermetallic alloys

Intermetallic alloys designed for their magnetic functionality often experience mechanical duress due to in-service stresses, which may impact their performance. Here, we investigate the impact of mechanical stresses leading to plastic deformation on the magnetic properties of the Heusler intermetallic alloy. Experimental magnetization measurements collected before and after grinding powders of the alloy demonstrate that the ferromagnetic saturation magnetization is dramatically impacted by crystalline defects imposed by mechanical stress. Density Functional Theory (DFT) γ-surfaces paired with Phase Field Dislocation Dynamics (PFDD) simulations predict that mechanical stresses lead to the formation of nano-scale planar defects that introduce a new environment hosting antiferromagnetic character. In situ micro-mechanical compression experiments were used to interrogate the orientation-dependent mechanical behavior of single crystals. Differential Phase Contrast Scanning Transmission Electron Microscopy (DPC STEM) performed for the deformed material reveals the local interplay between ferromagnetic domains and nano-scale planar defects resulting of plastic deformation.