Abstract
Using magneto-optical microscopy in combination with ellipsometry measurements, we show that all-optical switching with polarized femtosecond laser pulses in ferrimagnetic GdFeCo is subjected to a threshold fluence absorbed in the magnetic layer, independent of either the excitation wavelength or the polarization of the laser pulse. Furthermore, we present a quantitative explanation of the intensity window in which all-optical helicity-dependent switching (AO-HDS) occurs, based on magnetic circular dichroism. This explanation is consistent with all the experimental findings on AO-HDS so far, varying from single- to multiple-shot experiments. The presented results give a solid understanding of the origin of AO-HDS, and give novel insights into the physics of ultrafast, laser controlled magnetism.
Highlights
Controlling the magnetic state of a medium with the help of femtosecond laser pulses is a recently emerging and rapidly developing research direction in modern magnetism
Using magneto-optical microscopy in combination with ellipsometry measurements, we show that alloptical switching with polarized femtosecond laser pulses in ferrimagnetic GdFeCo is subjected to a threshold fluence absorbed in the magnetic layer, independent of either the excitation wavelength or the polarization of the laser pulse
We present a quantitative explanation of the intensity window in which all-optical helicity-dependent switching (AO-HDS) occurs, based on magnetic circular dichroism
Summary
Switching probability P as a function of the fluence at 1⁄4 700 nm for three different polarizations. The measurements with RC and LC pulses were performed at a different time than the ones with LP pulses, and the laser stability was different. Inset: Illustration of the switching probabilities in case of zero (solid) and nonzero (dashed) laser fluctuations using Eq (1). FLC and FRC denote the switching threshold of GdFeCo for LC and RC excitation pulses, respectively. Where is a unitless quantity representing the relative magnitude of the pulse-to-pulse laser fluctuation, which varies typically between 0.5%–2%
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