First principles investigation of domain walls and exchange stiffness in ferromagnetic Fe and antiferromagnetic NiMn

We investigate the domain walls in ferromagnetic Fe and antiferromagnetic NiMn with the first principles full-potential linearized augmented plane-wave method including intra-atomic noncollinear magnetism. In both cases, the self-consistent results demonstrate that the magnetization changes continuously from one orientation to another as seen in a Bloch wall. The formation energy of the domain wall (DeltaE(DW)) significantly decreases when the wall thickness increases, which leads to an exchange stiffness of 1.13x10(-11) J/m for Fe and 1.43x10(-11) J/m for NiMn. The predictions agree with those determined separately for Fe from a phenomenological calculation. (C) 2003 American Institute of Physics.