Tuning the magnetocrystalline anisotropy of rare-earth free L10-ordered Mn1-xTMxAl magnetic alloy (TM = Fe, Co, or Ni) with transition elements

Abstract

Tuning of the magnetocrystalline anisotropy of MnAl was studied by substituting Mn of MnAl with transition elements (Fe, Co, or Ni). The Brillouin function and semi-empirical Callen and Callen relation predicted the thermal behaviors of saturation magnetization and magnetocrystalline anisotropy energy. First-principles calculations based on density functional theory (DFT) were performed to calculate the electronic structures of Mn0.5TM0.5Al, where TM = Mn, Fe, Co, and Ni. The estimated total magnetic moment of Mn0.5TM0.5Al decreases as the number of valence electrons (n) of TM (e.g., 7 for Mn (3d5 4 s2), 8 for Fe (3d6 4 s2), 9 for Co (3d7 4 s2), and 10 for Ni (3d8 4 s2)) increases. Ni-substituted MnAl becomes ferrimagnetic, while other TM-substituted MnAl retain a ferromagnetic state. Curie temperature rapidly decreases with increasing the valence electrons from 685 K for MnAl to 20 K for Ni-substituted MnAl. Thermomagnetic behaviors of Mn0.5TM0.5Al (TM = Mn, Fe, Co, or Ni) are reported. Our magnetocrystalline anisotropy energy (MAE) calculations demonstrate that the magnetocrystalline anisotropy changes to the in-plane from the out-of-plane (uniaxial) direction for Co– and Ni-substituted MnAl. The K reaches a maximum of 2.98 MJ/m3 at n = 8, i.e., Fe substitution.