Signatures of relativistic spin-light coupling in ultrafast magneto-optical pump-probe experiments

Abstract

Femtosecond magneto-optical pump-probe measurements of ultrafast demagnetization show an intriguing difference in the first 100 fs of the magneto-optical Kerr response depending on whether the polarization of the pump and probe beams are in parallel or perpendicular configuration [Bigot et al., Nature Phys. 5, 515 (2009)]. Starting from a most general relativistic Hamiltonian we focus on the ultra-relativistic light-spin interaction and show that this coupling term leads to different light-induced opto-magnetic fields when pump and probe polarization are parallel and perpendicular to each other, providing thus an explanation for the measurements. We also analyze other pump-probe configurations where the pump laser is circularly polarized and the employed probe contains only linearly polarized light and show that similar opto-magnetic effects can be anticipated.

16 pages, 1 figure

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• Laser-induced torques in metallic ferromagnets
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Cited by in corpus (10)

• Relativistic theory of magnetic inertia in ultrafast spin dynamics
• Generalisation of Gilbert damping and magnetic inertia parameter as a series of higher-order relativistic terms
• Ultrafast demagnetization in ferromagnetic materials: Origins and progress
• Unified theory of magnetization dynamics with relativistic and nonrelativistic spin torques
• Terahertz spin dynamics driven by an optical spin-orbit torque
• Dynamics of the relativistic electron spin in an electromagnetic field
• Achiral dipoles on a ferromagnet can affect its magnetization direction
• Heisenberg representation of nonthermal ultrafast laser excitation of magnetic precessions
• Magnetization precession after non-collinear dual optical excitation
• Engineering spin-wave spectrum via the magnetization inertia tensor