Electronic structure and magnetic properties of L1_0 binary alloys

We present a systematic study of the magnetic properties of L1${}_0$ binary alloys FeNi, CoNi, MnAl and MnGa via two different density functional theory approaches. Our calculations show large magnetocrystalline anisotropies in the order $1{\text{MJ/m}}^3$ or higher for CoNi, MnAl and MnGa while FeNi shows a somewhat lower value in the range $0.48-0.77{\text{MJ/m}}^3$. Saturation magnetization values of $1.3\text{ MA/m}$, $1.0\text{ MA/m}$, $0.8\text{ MA/m}$ and $0.9\text{ MA/m}$ are obtained for FeNi, CoNi, MnAl and MnGa respectively. Curie temperatures are evaluated via Monte Carlo simulations and show $T_{\text{C}}=916\text{ K}$ and $T_{\text{C}}=1130\text{ K}$ for FeNi and CoNi respectively. For Mn-based compounds Mn-rich off-stoichiometric compositions are found to be important for the stability of a ferro or ferrimagnetic ground state with $T_{\text{C}}$ greater than $600\text{ K}$. The effect of substitutional disorder is studied and found to decrease both magnetocrystalline anisotropies and Curie temperatures in FeNi and CoNi.