Orbital and dipolar contributions to the hyperfine fields in bulk bcc Fe, hcp Co, and at the Fe/Ag(100) interface: The inclusion of orbital polarization

First-principles calculations can make quantitative predictions of many properties of solids including magnetic hyperfine fields (Bhf). The inclusion of relativistic effects becomes important in this case. We have selected to study three systems in order to assess the importance of orbital and dipolar contributions to the Bhf and its anisotropies: bulk bcc Fe, hcp Co, and the Fe/Ag(100) interface. For the last two, in-plane (parallel to the hexagonal planes and to the interface, respectively) and perpendicular magnetizations were considered. The influence of different exchange-correlation potentials (local density and generalized gradient approximation) and the inclusion of the orbital polarization term (known to improve the evaluation of orbital moments) in the Hamiltonian is reported. A comparison is made with other theoretical studies and to experiment when possible.