Unraveling Femtosecond Spin and Charge Dynamics with EUV T-MOKE Spectroscopy

Abstract

The magneto-optical Kerr effect (MOKE) in the extreme ultraviolet (EUV) regime has helped to elucidate some of the key processes that lead to the manipulation of magnetism on ultrafast timescales. However, as we show in this paper, the recently introduced spectrally-resolved analysis of such data can lead to surprising experimental observations, which might cause misinterpretations. Therefore, an extended analysis of the EUV magneto-optics is necessary. Via experimental determination of the dielectric tensor, we find here that the non-equilibrium excitation in an ultrafast magnetization experiment can cause a rotation of the off-diagonal element of the dielectric tensor in the complex plane. In direct consequence, the commonly analyzed magneto-optic asymmetry may show time-dependent behaviour that is not directly connected to the magnetic properties of the sample. We showcase such critical observations for the case of ultrafast magnetization dynamics in Ni, and give guidelines for the future analysis of spectrally-resolved magneto-optical data and its comparison with theory.

References in corpus (5)

• Super-Diffusive Spin-Transport as a Mechanism of Ultrafast Demagnetization
• Influence of laser-excited electron distributions on the x-ray magnetic circular dichroism spectra: Implications for femtosecond demagnetization in Ni
• Magneto-Optical Functions at the 3p resonances of Fe, Co, and Ni: Ab-initio description and experiment
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• Ultrafast element- and depth-resolved magnetization dynamics probed by transverse magneto-optical Kerr effect spectroscopy in the soft x-ray range

Cited by in corpus (4)

• Ultrafast demagnetization in ferromagnetic materials: Origins and progress
• Verification of ultrafast spin transfer effects in FeNi alloys
• Spectroscopic probe of ultrafast magnetization dynamics in the extreme ultraviolet spectral range
• Electronic mechanism of sub-100-fs demagnetization induced by a femtosecond light pulse