Realization of tetragonal Heusler alloy Mn3-xCrxGa for spintronic applications
Tetragonal Heusler alloys with high coercivity field (H C ), low saturation magnetic moment and high Curie temperature (T C ) have been considered as promising candidates for spin transfer torque (STT) applications. In this paper, tetragonal Heusler alloys Mn 3-x Cr x Ga have been designed and realized in experiments by adjusting the ratio of Mn/Cr and selecting suitable heat treatment conditions. It has been found that Mn 3-x Cr x Ga (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6 and 1) alloys exhibited multiple phase structures. As x > 0.5, both as-spun and as-annealed ribbons show pure B2-type body-centered cubic (b.c.c.) structure. The D0 22 -type tetragonal Heusler structure starts to appear in the matrix of cubic B2 structure as x = 0.5 in as-annealed ribbon samples, and gradually develops to pure tetragonal structure as x = 0.3. There is a significant structure difference between as-annealed and as-spun ribbons as x ≤ 0.2. Cu 3 Au-type face-centered cubic (f.c.c.) structure is observed for as-spun ribbons, while the annealed ribbons show pure tetragonal structure. The pure tetragonal Heusler alloys have hard-ferrimagnetic properties with Hc higher than 258 kA/m, accompanied by a high T C , large magnetic remanence (B r ) and low magnetic moment at room temperature, which are important factors for spin-transfer torque applications. Our work reveals the tunability of the magnetic and structural properties of Heusler alloys by changing the ratio of doping elements, providing a guidance for further searching for tetragonal Heusler alloys.