Unveiling the Magnetic and Structural Properties of (X 2 YZ; X = Co and Ni, Y = Fe and Mn, and Z = Si) Full-Heusler Alloy Microwires with Fixed Geometrical Parameters.

We studied Ni₂FeSi-, Co₂FeSi-, and Co₂MnSi-based full-Heusler alloy glass-coated microwires with the same geometric parameters, i.e., fixed nucleus and total diameters, prepared using the Taylor–Ulitovsky method. The fabrication of X₂YZ (X = Co and Ni, Y = Fe and Mn, and Z = Si)-based glass-coated microwires with fixed geometric parameters is quite challenging due to the different sample preparation conditions. The XRD analysis showed a nanocrystalline microstructure for all the samples. The space groups Fm3¯m (FCC) and Im3¯m (BCC) with disordered B2 and A2 types are observed for Ni₂FeSi and Co₂FeSi, respectively. Meanwhile, a well-defined, ordered L2₁ type was observed for Co₂MnSi GCMWs. The change in the positions of Ni, Co and Mn, Fe in X₂YSi resulted in a variation in the lattice cell parameters and average grain size of the sample. The room-temperature magnetic behavior showed a dramatic change depending on the chemical composition, where Ni₂FeSi MWs showed the highest coercivity (H_c) compared to Co₂FeSi and Co₂MnSi MWs. The H_c value of Ni₂FeSi MWs was 16 times higher than that of Co₂MnSi MWs and 3 times higher than that of Co₂FeSi MWs. Meanwhile, the highest reduced remanence was reported for Co₂FeSi MWs (Mr = 0.92), being about 0.82 and 0.22 for Ni₂FeSi and Co₂MnSi MWs, respectively. From the analysis of the temperature dependence of the magnetic properties (H_c and M_r) of X₂YZ MWs, we deduced that the H_c showed a stable tendency for Co₂MnSi and Co₂FeSi MWs. Meanwhile, two flipped points were observed for Ni₂FeSi MWs, where the behavior of H_c changed with temperature. For M_r, a monotonic increase on decreasing the temperature was observed for Co₂FeSi and Ni₂FeSi MWs, and it remained roughly stable for Co₂MnSi MWs. The thermomagnetic curves at low magnetic field showed irreversible magnetic behavior for Co₂MnSi and Co₂FeSi MWs and regular ferromagnetic behavior for Ni₂FeSi MWs. The current result illustrates the ability to tailor the structure and magnetic behavior of X₂YZ MWs at fixed geometric parameters. Additionally, a different behavior was revealed in X₂YZ MWs depending on the degree of ordering and element distribution. The tunability of the magnetic properties of X₂YZ MWs makes them suitable for sensing applications. [ABSTRACT FROM AUTHOR]