Magnetism-structure triple point morphotropic phase boundary and resulting W-type magnetostrictive effect in Ni50Mn34Sb16−xGax Heusler alloys

Abstract

The mutual coupling of structure and magnetism is crucial for Heusler alloys. In this paper, Ni₅₀Mn₃₄Sb_16−xGa_x (0 ≤ x ≤ 16) alloys were prepared by arc melting. Based on the test results of structure and magnetism, the magnetic-structural phase diagram of Ni₅₀Mn₃₄Sb_16−xGa_x (0 ≤ x ≤ 16) was drawn. The structure changes from cubic to monoclinic and finally to tetragonal as the x increases at room temperature. Its phase diagram shows a morphotropic phase boundary (MPB) starting from a tricritical triple point (around the Ni₅₀Mn₃₄Sb₅Ga₁₁ alloy) of a cubic paramagnetic phase, ferromagnetic monoclinic, and antiferromagnetic tetragonal phases. And Ni₅₀Mn₃₄Sb₅Ga₁₁ alloy has experienced five different phase states: paramagnetic austenite → ferromagnetic austenite → antiferromagnetic martensite → ferromagnetic martensite → spin glass as the temperature decreased. Further study of the alloys’ magnetostrictive properties near the MPB showed that as x increases, a negative strain initially appears, followed by a W-type that crosses negative and positive strains, and then a positive strain. This is caused by the inconsistency in the speed and degree of magnetic domain walls response with monoclinic and tetragonal coexisting structures. This indicates that coupling between structure and magnetism is critical to the properties of materials. This work provides valuable insights into the magnetostrictive behavior and structural evolution of Heusler alloys, particularly in the context of MPB systems, and offers guidance for the design and optimization of material properties through controlled magnetic-structural interactions.Kindly check and confirm the edit made in the title.The edit made in the title has been confirmed to be accurate.

Graphical abstract