Superhigh Magnetostriction in Non‐Equilibrium Grown Fe‐Ga Single‐Crystals by Rapid‐Directional‐Solidification

The non-equilibrium microstructure characterized by Tb supersaturation within Fe-Ga single-crystals is deduced to induce a substantial enhancement in magnetostriction. However, the growth of the non-equilibrium single-crystal remains a formidable obstacle, as existing methods can only produce either non-equilibrium polycrystal or near-equilibrium single-crystal, leading to the stagnation in magnetostriction. Herein, a rapid-directional-solidification (RDS) strategy is devised to grow non-equilibrium single-crystals. The RDS is realized through achieving an ultrahigh temperature gradient of ≈10⁶ K m^-1 at S-L interface front, accompanied by an ultrafast growth velocity. This results in single-crystal growth under non-equilibrium conditions with a giant cooling rate of 10²-10³ K s^-1, which is ≈1-2 orders of magnitude greater than the current state-of-the-art of directional-solidification methods. A non-equilibrium Fe-Ga single-crystal, featured with traces of Tb supersaturation, is successfully grown with a significantly enhanced magnetostriction of 489 ppm. This magnitude of magnetostriction sets a record in bulk Fe-Ga materials, surpassing the maximum value reported for Fe-Ga single-crystals by 60%. The advent of RDS strategy opens an avenue for fabricating non-equilibrium single-crystals with revolutionary performance, and paves the way for fabricating currently unattainable single-crystals for engineering applications.