Nanoscale Mapping of Ultrafast Magnetization Dynamics with Femtosecond Lorentz Microscopy

Abstract

Novel time-resolved imaging techniques for the investigation of ultrafast nanoscale magnetization dynamics are indispensable for further developments in lightcontrolled magnetism. Here, we introduce femtosecond Lorentz microscopy, achieving a spatial resolution below 100 nm and a temporal resolution of 700 fs, which gives access to the transiently excited state of the spin system on femtosecond timescales and its subsequent relaxation dynamics. We demonstrate the capabilities of this technique by spatio-temporally mapping the light-induced demagnetization of a single magnetic vortex structure and quantitatively extracting the evolution of the magnetization field after optical excitation. Tunable electron imaging conditions allow for an optimization of spatial resolution or field sensitivity, enabling future investigations of ultrafast internal dynamics of magnetic topological defects on 10-nanometer length scales.Aiming for higher bit densities, manipulation of magnetization on the nanoscale is a key aspect for future information processing and storage applications. In recent years, significant achievements on controlling magnetic domains and topological defects †

Generation and Characterization of Attosecond Microbunched Electron Pulse Trains via Dielectric Laser Acceleration

“…Ultrashort electron pulses find various applications in research and technology, including ultrafast diffraction [1][2][3], ultrafast electron microscopy [4][5][6][7], as well as ultrafast photon generation [8]. Many of these techniques operate with electron pulse durations in the realm of femtoseconds.…”

“…The temporal resolution of lasertriggered electron sources is usually limited by the temporal duration of the electron-releasing laser pulses and subsequent dispersive broadening of the electron pulses. Typical electron pulse durations at the sample are in the range of 30 fs to 1 ps [1][2][3][4][5][6][7][8][9]. Schemes have been proposed and demonstrated to compress the electron pulses at the sample, see for example [10,11].…”

Sub-100 nanosecond temporally resolved imaging with the Medipix3 direct electron detector

“…This has enabled the specialised field of ultra-fast electron microscopy (UEM) in which the illumination duration is of the order of the femtosecond laser pulse duration [4,5,6,7,8]. Utilising a pump-probe imaging methodology for the study of repeatable phenomena has led to insights in areas such as nanophotonics [9], atomic structural dynamics [10], magnetic dynamics [11], and even electron dynamics [12]. Stochastic, non-repeatable, processes have also been studied using high intensity, nanosecond duration laser pulses in dynamic TEM (DTEM).…”

Coulomb interactions in high-coherence femtosecond electron pulses from tip emitters

“…The concept of tip-shaped electron sources has therefore been adopted for pulsed photoemitters with nm-sized emission areas 16,41–48 . The increased coherence properties of such tip-emitted electron pulses and their application for locally probing ultrafast phenomena were recently demonstrated for the quantum coherent optical control of free-electron states 49 and the nanoscale mapping of ultrafast structural 25 and magnetic dynamics 50 …”