Realization of multifunctional shape-memory ferromagnets in all-<i>d</i>-metal Heusler phases

TLDR

Heusler ferromagnetic shape‑memory alloys typically combine transition‑metal d‑elements with main‑group p‑elements. This study demonstrates that fully d‑metal Heusler phases can be fabricated as functional shape‑memory alloys. By incorporating Ti into NiMn to form a cubic B2 Heusler phase and further doping Co to induce ferromagnetism, the authors achieved a tunable martensitic transformation temperature and magnetic‑field‑induced multifunctional behavior in Ni(Co)–Mn–Ti alloys, showing that d metals alone can stabilize the B2 phase, promote strong ferromagnetic coupling, and enable controllable shape‑memory effects.

Abstract

Heusler ferromagnetic shape-memory alloys (FSMAs) normally consist of transition-group d-metals and main-group p-elements. Here, we report the realization of FSMAs in Heusler phases that completely consist of d metals. By introducing the d-metal Ti into NiMn alloys, cubic B2-type Heusler phase is obtained and the martensitic transformation temperature is decreased efficiently. Strong ferromagnetism is established by further doping Co atoms into the B2-type antiferromagnetic Ni-Mn-Ti austenite. Based on the magnetic-field-induced martensitic transformations, collective multifunctional properties are observed in Ni(Co)-Mn-Ti alloys. The d metals not only facilitate the formation of B2-type Heusler phases, but also establish strong ferromagnetic coupling and offer the possibility to tune the martensitic transformation.