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arXiv · 1504.07915

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

Ritwik Mondal·Marco Berritta·Karel Carva·Peter M. Oppeneer
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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 ($\leq 0.1$%) to the laser-induced magnetization change in Ni.

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Ritwik Mondal, Marco Berritta, Karel Carva, Peter M. Oppeneer. 2015-04-30. Ab initio investigation of light-induced relativistic spin-flip effects in magneto-optics. https://doi.org/10.1103/physrevb.91.174415

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