Highly Stable Magnetostriction in Nanoheterogeneous Fe₈₁Ga₁₉ Alloy Enabled by Uncoarsening of Nanoprecipitates Due to Negative Interfacial Energy

Abstract Nanoprecipitates are crucial for determining diversse properties of nanoheterogeneous materials. For instance, the tetragonal L6₀ nanoprecipitates dispersing in the body‐centered cubic A2 matrix yield the large magnetostrictive effect in Fe‐Ga alloys. Nanoprecipitates are usually coarsened under thermally activated circumstances in most of nanoheterogenous materials, which typically leads to the degeneration of the material performance. This is a bottleneck issue for the long‐time usage of nanoheterogeneous materials under thermally activated conditions. In this study, it is found that the L6₀ nanoprecipitates in large‐magnetostriction Fe₈₁Ga₁₉ single crystals are superiorly stable under accelerating aging experiments, as evidenced by the almost unchanged phase structure, average size, volume fraction and tetragonality. Accordingly, the large magnetostrictive effect is highly stable upon long‐time thermal excitations. Systematic studies combing experimental and theoretical efforts reveal that the stronger chemical bonding between the L6₀ nanoprecipitates and the A2 matrix relative to the original chemical bonding within the A2 matrix results in a strikingly negative interfacial energy that stabilizes the nanoprecipitates. Thus, this work provides a promising strategy for stabilizing nanoprecipitates via interfacial chemical bonding strengthening induced negative interfacial energy and hence achieving highly stable performance of nanoheterogeneous materials.