The structural phase transformation in a non-stoichiometric shape memory Fe_42.8Mn_27.6Ga_29.6 Heusler glass-coated microwire was experimentally observed using indirect magnetic, permeability, and electrical resistance measurements. While the temperature dependence of magnetization revealed hysteresis of magnetization during the heating and cooling process, magnetic hysteresis loops point to the change in the direction of the easy magnetization axis of the low- and high-temperature phase. Additionally, the unusual behavior of the permeability and electrical resistance measurements are in good agreement with the magnetic measurements. The x-ray diffraction profile measured at room temperature revealed the coexistence of a high-temperature L2₁ phase (a= 5.88 Å) and low-temperature phase with the L1₂ structure (a = 3.71 Å) and can be considered as another proof of the shape memory effect that is expected in the Fe–Mn–Ga-based Heusler alloys. In the presented glass-coated microwire, it is not only possible to shift the transformation temperature with the external magnetic field, but from its initial permeability value, it is possible to determine whether the alloy has undergone the structural transformation. Therefore, the presented Fe–Mn–Ga-based glass-coated microwire may be considered a suitable candidate for microactuators with sensory capabilities.

In this article, the downsizing of functional Heusler alloys is discussed, focusing on the published results dealing with Heusler alloy nanowires. The theoretical information inspired the fabrication of novel nanowires that are presented in the results section of the article. Three novel nanowires were fabricated with the compositions of Ni₆₆Fe₂₁Ga₁₃, Ni₅₈Fe₂₈In₁₄, and Ni₅₀Fe₃₁Sn₁₉. The Ni₆₆Fe₂₁Ga₁₃ nanowires were fabricated, aiming to improve the stoichiometry of previous functional Ni-Fe-Ga Heusler nanomaterials with a functional behavior above room temperature. They exhibit a phase transition at the temperature of ≈375 K, which results in a magnetocaloric response of |ΔS_M| ≈ 0.12 J·kg⁻¹·K⁻¹ at the magnetic field change of only μ₀ΔH = 1 T. Novel Heusler alloy Ni₅₈Fe₂₈In₁₄ nanowires, as well as Ni₅₀Fe₃₁Sn₁₉ nanowires, are analyzed for the first time, and their magnetic properties are discussed, introducing a simple electrochemical approach for the fabrication of nanodimensional alloys from mutually immiscible metals.