Ab-initio description of the magnetic shape anisotropy due to the Breit interaction

A quantum-mechanical description of the magnetic shape anisotropy, that is usually ascribed to the classical magnetic dipole–dipole interaction, has been developed. This is achieved by including the Breit interaction, that can be seen as an electronic current–current interaction in addition to the conventional Coulomb interaction, within fully relativistic band structure calculations. The major sources of the magnetic anisotropy, spin–orbit coupling and the Breit interaction, are treated coherently this way. This seems to be especially important for layered systems for which often both sources contribute with opposite sign to the magnetic anisotropy energy. Applications to layered transition metal systems are presented to demonstrate the implications of this new approach in treating the magnetic shape anisotropy.