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

Abstract 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 ≈10 6 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 10 2 –10 3 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.