First-principles electronic structure studies based on local spin density functional theory and performed on extremely complex simulations of ever increasingly realistic systems, play a very important role in explaining and predicting surface and interface magnetism. This has led to solving even more challenging problems like the embrittlement of the Fe grain boundary, discussed here. Now, a major issue for first-principles theory is the treatment of the weak spin-orbit coupling (SOC) in magnetic transition metals and their alloys and its subsequent effects: (i) A major breakthrough in eliminating the numerical randomness for the determination of the magneto-crystalline anisotropy was made with the state-tracking and torque approaches. This now enables us to treat magnetostriction and its inverse effect, strain-induced magnetic anisotropy in transition metal bulk, thin films and alloys, (ii) The magneto-optical Kerr effects and x-ray magnetic circular dichroism are now directly calculated and compared with experiment. In all this work, and more recently, on the first-principles calculations of giant magneto-resistance in multilayers, extensive first-principles calculations and model analyses provide simple physical insights and guidelines to search for new magnetic recording and sensor materials.

In the exciting field of low dimensional magnetic systems including surfaces, interfaces and thin-films, local spin density (LSD) functional ab initio electronic structure calculations have played a key role by not only providing a clearer understanding of the experimental observations but also predicting new systems with desired properties. Our extensive calculated results demonstrate that: (i) Magnetic clean surfaces or interfaces with inert substrates undergo strong magnetic moment enhancements; (ii) the strong interaction with nonmagnetic transition metals diminishes (completely in some cases) the ferromagnetism and usually stabilizes the antiferromag-netic configuration. By including spin-orbit coupling as a perturbation, (i) reliable results for the Magneto-crystalline anisotropy of ultra-thin films can be obtained using the state-tracking procedure, although the anisotropy energy is a few tenths of a MeV; (ii) spectra of the Magneto-optical Kerr effects and magnetic circular dichroism in the soft x-ray region can be determined.

Using the all-electron full potential linearized augmented plane wave (FLAPW) total energy method, the influence of P impurity atoms on the cohesion of the Fe Σ3[1$\overline 1$10](111) grain boundary is studied through direct comparison of phosphorus/iron interactions in the grain boundary and free surface environments. The calculated nearest P–Fe distance in P/Fe(111) is 2.14 Å—amounting to a 5% contraction compared to that (2.26 Å) measured for the Fe3P compound and assumed for the P–Fe grain boundary. The polar-covalent P–Fe chemical bonding, which is a strong function of the P–Fe interatomic distance, is thus stronger on the Fe(111) surface, while P reduces the spin polarization of the surrounding Fe atoms more efficiently in the grain boundary environment. These effects are examined in terms of the relative segregation energies affecting the work of boundary fracture.