Laser-Induced Demagnetization at Ultrashort Time Scales: Predictions of TDDFT

Time-dependent density functional theory (TDDFT) is implemented in an all electron solid-state code for the case of fully unconstrained noncollinear spins. We use this to study intense, short, laser pulse-induced demagnetization in bulk Fe, Co, Ni and find that demagnetization can take place on time scales of <20 fs. It is demonstrated that this form of demagnetization is a two-step process: excitation of a fraction of electrons followed by spin-flip transitions mediated by spin orbit coupling of the remaining localized electrons. We further show that it is possible to control the moment loss by tunable laser parameters, including frequency, duration, and intensity.