High speed algorithm for the calculation of magnetic and orbital excitations in rare earth based systems

An algorithm for the efficient and fast calculation of dispersive magnetic excitations in rare earth based systems has been developed. Crystal field anisotropy and anisotropy of the two ion interactions can be taken into account. It is based on the standard mean field-random phase approximation of the problem. In analogy to lattice dynamical calculations the central problem of finding the poles of the dynamical susceptibility χ(Q, ω) has been reduced to the diagonalisation of a dynamical matrix. This approach is applicable to complex magnetic structures, it is fast and easily generalised to include many single ion transitions and orbital interactions.