The magnetic Hamiltonian of ${\mathrm{Nd}}_2$${\mathrm{Fe}}_{14}$B at the Nd site has been constructed using a first-principles approach based on the energy-band results. The crystal-field parameters are evaluated using the real-space charge-density distribution and the exchange field is obtained by applying an approximate Stoner model to the spin-polarized density of states. The calculated stabilization energy is in good agreement with the experimental measurement. It is also shown that the exchange field predominates in the magnetic Hamiltonian but the fourth-order and second-order off-diagonal crystal-field terms are not entirely negligible.

• Received 14 April 1989

DOI:https://doi.org/10.1103/PhysRevB.40.5292