Unifying ultrafast magnetization dynamics

The authors present a microscopic model that successfully explains the ultrafast equilibration of magnetic order in ferromagnetic metals at a time scale tM of only a few hundred femtoseconds after pulsed laser excitation. tM Can be directly related to the so-called Gilbert damping factor a that describes damping of GHz precessional motion of the magnetization vector. Independent of the spin-scattering mechanism, an appealingly simple equation relating the two key parameters via the Curie temp. TC is derived, tM~c0[planck]/kBTCa, with [planck] and kB the Planck and Boltzmann consts., resp., and the prefactor c0.apprx.(1)/(4). The authors argue that phonon-mediated spin-flip scattering may contribute significantly to the sub-ps response. [on SciFinder (R)