Electronic Structure and Maximum Energy Product of MnBi

We have performed first-principles calculations to obtain magnetic moment, magnetocrystalline anisotropy energy (MAE), i.e., the magnetic crystalline anisotropy constant (K), and the Curie temperature (T-c) of low temperature phase (LTP) MnBi and also estimated the maximum energy product (BH)(max) at elevated temperatures. The full-potential linearized augmented plane wave (FPLAPW) method, based on density functional theory (DFT) within the local spin density approximation (LSDA), was used to calculate the electronic structure of LPM MnBi. The T-c was calculated by the mean field theory. The calculated magnetic moment, MAE, and T-c are 3.63 mu(B)/f.u. (formula unit) (79 emu/g or 714 emu/cm(3)), -0.163 meV/u.c. (or K = -0.275 x 10(6) J/m(3)) and 711 K, respectively. The (BH)(max) at the elevated temperatures was estimated by combining experimental coercivity (H-ci) and the temperature dependence of magnetization (M-s(T)). The (BH)(max) is 17.7 MGOe at 300 K, which is in good agreement with the experimental result for directionally-solidified LTP MnBi (17 MGOe). In addition, a study of electron density maps and the lattice constant c/a ratio dependence of the magnetic moment suggested that doping of a third element into interstitial sites of LTP MnBi can increase the M-s.