The Magnetism of Mn$_{\mathrm{2-x}}$Fe$_{\mathrm{x}}$B Alloys : First-Principles Calculations

Magnetic, electronic and structural properties of Mn$_{\mathrm{2-x}}$Fe$_{\mathrm{x}}$B (0 $\le $ x $\le $ 2) are investigated by the First principles calculations with the virtual crystal approximation (VCA) based on the density-functional theory (DFT) with generalized gradient approximation (GGA). Although both of Mn$_{\mathrm{2}}$B and Fe$_{\mathrm{2}}$B have the same electronic structure of I4/MCM with different lattice constants, the former is anti-ferromagnetic and the latter ferromagnetic. All calculations, based on the four types of magnetic states of NM (non-magnetic), FM (ferromagnetic), AFM1 and AFM2 (anti-ferromagnetic), illustrate that there is a critical point of magnetic phase transition occurred at x as 0.5 from AFM2 to FM state under the condition of the lowest energy. Results are also in agreement with the Stoner model within the range of FM state.