Triple point-type morphotropic phase boundary in ferromagnetic (1 − x )TbFe2– x NdFe2 system and corresponding magnetoelastic response

The morphotropic phase boundary (MPB) phenomenon plays a pivotal role in ferromagnetic systems for achieving field-induced enhancement of magnetoelastic responses. However, conventionally titled MPBs often show inferior temperature stability, resulting in significant degradation of magnetoelastic performance over broad temperature ranges. In this work, we designed a vertical phase boundary between the tetragonal and rhombohedral phases in the ferromagnetic (1 − x)TbFe2–xNdFe2 system, originating from a structural triple point (xTP). At the MPB composition (xMPB), large low-field magnetostriction, narrow magnetic hysteresis, and minimal magnetocrystalline anisotropy were simultaneously achieved at room temperature. In situ high-resolution transmission electron microscopy (HRTEM) revealed the coexistence of nanoscale rhombohedral and tetragonal magnetic domains (