Interatomic magnetic interactions in iron

We have performed total-energy calculations for bcc iron in several magnetic structures using density-functional theory. The lattice constant was fixed at its experimental value. We have considered the ferromagnetic and several antiferromagnetic configurations and used the calculated total energies to obtain the interaction parameters up to sixth nearest neighbors in a Heisenberg model. We assumed that the local density functional describing exchange and correlation is the same for the ferromagnetic ground state and the antiferromagnetic states, with the latter corresponding to local minima of the energy functional. In this approach, the interatomic magnetic interactions are pure hybridization effects, due to the kinetic energy term in the total energy. Our parametrized model Heisenberg Hamiltonian yields realistic values of the spin stiffness constant and the critical temperature.