Ab initio investigation of light-induced relativistic spin-flip effects in magneto-optics

Abstract

Excitation of a metallic ferromagnet such as Ni with an intensive femtosecond laser pulse causes an ultrafast demagnetization within approximately 300 fs. It was proposed that the ultrafast demagnetization measured in femtosecond magneto-optical experiments could be due to relativistic light-induced processes. We perform an ab initio investigation of the influence of relativistic effects on the magneto-optical response of Ni. To this end, we develop, first, a response theory formulation of the additional appearing ultra-relativistic terms in the Foldy-Wouthuysen transformed Dirac Hamiltonian due to the electromagnetic field, and, second, compute the influence of relativistic light-induced spin-flip transitions on the magneto-optics. Our ab initio calculations of relativistic spin-flip optical excitations predict that these can give only a very small contribution ($\le 0.1$%) to the laser-induced magnetization change in Ni.

10 pages, 3 figures, Accepted for publication in Physics Review B

References in corpus (4)

• Super-Diffusive Spin-Transport as a Mechanism of Ultrafast Demagnetization
• Ab initio theory of electron-phonon mediated ultrafast spin relaxation of laser-excited hot electrons in transition-metal ferromagnets
• Exchange relaxation as the mechanism of ultrafast spin reorientation in two-sublattice ferrimagnets
• Lagrangian approach to the semi-relativistic electron dynamics in the mean-field approximation

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