Exchange interaction parameters and adiabatic spin-wave spectra of ferromagnets: a "renormalized magnetic force theorem".

The "magnetic force theorem" is frequently used to compute exchange interaction parameters and adiabatic spin-wave spectra of ferromagnets. The interest of this approach is that it allows one to obtain these results from a non-self-consistent calculation of the (single-electron) band energy only, which greatly reduces the computational effort. However, as discussed by various authors, this approach entails some systematic error. Here, a "renormalized magnetic force theorem" allows us to remove this systematic error without significantly increasing the computational effort involved. For systems with one atom per unit cell, it amounts to a simple renormalization of the spin-wave spectrum.