A first principles theory of magnetocrystalline anisotropy in metals

A first-principles theory of the zero-temperature magnetocrystalline anisotropy in metals is discussed. It is based on a relativistic spin-polarised multiple-scattering theory. The magnetic moment can point along any direction with respect to the crystal lattice and the total energy is calculated. The difference between total energies for two different moment directions is the magnetocrystalline anisotropy energy. The authors show that this energy difference can be written as the difference in single-particle energies for the same charge density. The theory is illustrated with a calculation of the anisotropy in energy and spin contribution to the magnetic moment in nickel. It is found that the theory gives good qualitative agreement with experiment in this case. Numerical difficulties involved in the calculation are discussed.