Thomas Olsen - Magnetic spectroscopies - extracting ground state magnetic order and magnons from DFT

Abstract I will go through the basic DFT approaches for extracting ground state magnetic order as well as magnetic excitation spectra. First, the ground state order is discussed and it is shown that it may be determined from spin spiral calculations within the generalized Bloch theorem. Although this is in principle a systematic approach, it cannot accomodate spin-orbit interactions and the inclusion of these for extrcating spin orientation will be discussed. In the second part I discuss magnetic excitations, which can be exytractred from beyond DFT methods. In particular, I will discuss the, magnetic force theorem, time-dependent density functional theory and the Bethe-Salpeter equation for magnons. While the latter two may produce accurate results that included Landau damping and mode branching in metals, only the MFT is straightforward to apply routinely for easy comparison with INS measurements.