Magnetic domain reconfiguration enabled uniform magnetostriction in Fe₈₁Ga₁₉ single crystals grown under large temperature gradient

The relationship between the uniformity of magnetostriction and magnetic domain structure in Fe₈₁Ga₁₉ single crystals grown under a large temperature gradient was meticulously examined. Remarkably, the as-grown single crystals exhibited a substantial nonuniformity of magnetostriction, with fluctuations reaching ±54 ppm. Notably, stress aging for 1 h significantly reduced the magnetostriction nonuniformity to ±15 ppm. Structural analysis revealed no discernible differences in the composition or nanoheterogeneous microstructure before and after stress aging. However, in the as-grown single crystals, irregular and fine magnetic domains, with widths varying from several microns to less than 100 microns, were observed. Intriguingly, some stubborn magnetic domains remained unrotated during the magnetostriction measurements, contributing to the observed nonuniformity. This was further corroborated by the nonuniform local hysteresis loops measured at different locations. Two-dimensional X-ray diffraction analysis confirmed that this special magnetic domain structure was associated with the presence of inhomogeneous internal stresses within the as-grown crystals. Stress aging effectively released these inhomogeneous internal stresses, eliminating the stubborn magnetic domains. Phase field simulations were employed to establish a comprehensive understanding of the interplay between the internal stress state, magnetic domain structure, and magnetostriction uniformity. These simulations provided a robust framework for interpreting the experimental observations and underscoring the significance of stress aging in enhancing the magnetostriction uniformity. The achieved highly uniform magnetostriction will be beneficial for highly efficient applications of the Fe₈₁Ga₁₉ single crystals in actuators, sensors and transducers. This work supplies a strategy of magnetic domain reconfiguration to improve the magnetostriction uniformity of material.