Giant heterogeneous magnetostriction induced by charge accumulation-mediated nanoinclusion formation in dual-phase nanostructured systems

The fundamental origin of giant magnetostriction in dual-phase nanostructured systems is still under debate in recent years. Previous studies have revealed that the formation of tetragonal nanoinclusions induced the enlargement in local magnetocrystalline anisotropy, leading to a strengthened magneto–elastic coupling coefficient, which was considered to promote magnetostriction. Another key factor of magnetostriction, the influence of the nanoinclusions on the elastic constants of the lattices is, however, still not clear. In this work, we propose a mechanism based on the experimental and theoretical results of binary and rare-earth (RE) doped FeGa single-crystals. Doping traces of RE atoms effectively increase the density of nanoinclusions in the A2 matrix, due to the high selectivity of RE atoms they possess stronger bonding interaction with Fe atoms rather than Ga atoms. As a consequence, the elastic constant c₁₂ significantly increases with the rising density of tetragonal nanoinclusions as opposed to the constant c₁₁, resulting in a remarkable enhancement in magnetostriction due to the immediate relevance between magnetostriction (λ₀₀₁) and c₁₁−c₁₂. A superior magnetostriction of 390 ppm is obtained in the RE-doped single-crystal due to lattice softening induced by the nanoinclusions. This uncovered mechanism sheds light onto the contribution of RE atoms on the magnetostriction in FeGa single-crystals, and establishes a foundation for developing new-generation dual-phase magnetostrictive materials with unprecedented levels of magnetostriction.