Magnetocrystalline anisotropy regulations in bulk L1₀-MnGa alloys by tailoring the tetragonal lattice parameter c: Selectively alloying Al and C atoms

Previous theoretical calculations have proved that the magnetocrystalline anisotropy constant (K_u) of tetragonal MnGa alloys is closely dependent on the lattice parameter c, while it is insensitive to the lattice parameter a. Motivated by this information, selectively alloying the substitutional Al element and the interstitial C element was performed for Mn₅₄Ga₄₆ alloy to regulate K_u by tailoring the lattice parameter c. c was decreased from 3.7030 Å to 3.6908 Å and K_u was increased from 1.673 MJ m⁻³ to 1.777 MJ m⁻³ by the substitution of 4 at% Al for Ga. Although c could be continuously decreased by increasing the content of Al, K_u was almost unchanged. The underlying mechanism was discussed by performing first-principles calculations. Reversely, c was increased to 3.7136 Å and K_u was decreased to 1.573 MJ m⁻³ by doping 2 at% C. The lattice parameter a kept almost constant in both the MnGaAl and MnGaC alloys. This work confirmed that the anisotropy field H_a of Mn₅₄Ga₄₆ alloy could be flexibly regulated from 3.97 T to 5.41 T by alloying with Al or C elements.