Abstract
Ultrafast magnetization reversal driven by femtosecond laser pulses has been shown to be a promising way to write information. Seeking to improve the recording density has raised intriguing fundamental questions about the feasibility of combining ultrafast temporal resolution with sub-wavelength spatial resolution for magnetic recording. Here we report on the experimental demonstration of nanoscale sub-100 ps all-optical magnetization switching, providing a path to sub-wavelength magnetic recording. Using computational methods, we reveal the feasibility of nanoscale magnetic switching even for an unfocused laser pulse. This effect is achieved by structuring the sample such that the laser pulse, via both refraction and interference, focuses onto a localized region of the structure, the position of which can be controlled by the structural design. Time-resolved photo-emission electron microscopy studies reveal that nanoscale magnetic switching employing such focusing can be pushed to the sub-100 ps regime.
Highlights
Ultrafast magnetization reversal driven by femtosecond laser pulses has been shown to be a promising way to write information
Of particular interest to magnetic recording applications is the magnetization reversal induced by a single femtosecond laser pulse, which was first reported in GdFeCo ferrimagnetic amorphous alloys[14]
Using finite-difference timedomain (FDTD) methods to simulate the laser absorption profile within the magnetic structure, we reveal the feasibility of nanoscale magnetic switching even for the case of an unfocused incoming laser pulse
Summary
Ultrafast magnetization reversal driven by femtosecond laser pulses has been shown to be a promising way to write information. We reveal the feasibility of nanoscale magnetic switching even for an unfocused laser pulse This effect is achieved by structuring the sample such that the laser pulse, via both refraction and interference, focuses onto a localized region of the structure, the position of which can be controlled by the structural design. Using finite-difference timedomain (FDTD) methods to simulate the laser absorption profile within the magnetic structure, we reveal the feasibility of nanoscale magnetic switching even for the case of an unfocused incoming laser pulse This effect originates from the laser pulse coupling and propagating within the magnetic structure where it experiences a complex combination of refraction and interference that leads to its focusing onto a localized region of the structure. Time-resolved studies with the help of photoemission electron microscopy (PEEM), using X-ray magnetic circular dichroism (XMCD) as a contrast mechanism in magnetic structures down to 1 mm  1 mm, clearly reveal that the subwavelength AOS employing the focusing properties of the structure can be pushed into sub-100 ps regime
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