Time-dependent Liouville density functional investigation of ultrafast demagnetization

Laser-induced ultrafast demagnetization in ferromagnetic 3d
(1) and 4f metals (2) has been a focus of investigation over a
decade. However, to describe it theoretically has been challenging.
We apply our newly-developed time-dependent Liouville density
functional theory (3,4) to both transition metals and rare-earth
metals and find it very successful. The theory shows that with a
strong laser field, the demagnetiation time becomes longer, and both
the majority and minority bands are shifted. In rare-earth metails,
it yields the exchange interaction shift which matches the
experimental results semi-quantitatively. For thin films, the
demagnetization indeed becomes stronger. This matches the
time-dependent density functional theory results, but obeys the Pauli
exclusion principle. We also find that the spin transport effect is
very weak in ferromagnetic nickel (5).

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