Angular momentum redistribution in laser-induced demagnetization

The dynamics of ultrafast demagnetisation in 3$d$ magnets is complicated by the presence both spin ${\v S}$ and orbital L}$ angular momentum, with microscopic mechanism which magnetic moment redistributed to lattice, at what time scales, yet be resolved. Employing state-of-the-art dependent density function theory we disentangle these two momenta. Utilising ultra short (5~fs) pulses that separate spin-orbit (SO) direct optical excitation demonstrate a two-step mechanism: (i) an initial loss due laser excitation, followed post pulse (ii) increase as transfers during subsequent ($> 15$~fs) SO induced spin-flip demagnetisation. We also show see unambiguous transfer required.