Imaging Magnetic Dynamics with <i>In Situ</i> and Ultrafast Lorentz Transmission Electron Microscopy

Magnetic microscopy based on the magneto-optic Kerr effect (MOKE) can offer femtosecond temporal resolution of magnetic dynamics, but limited spatial resolution. On the other hand, a spatial resolution on the order of ten nanometers is possible when imaging with X-ray magnetic circular dichroism (XMCD), but temporal resolution is limited to ten picoseconds at best at synchroton beamlines. Lorentz transmission electron microscopy (LTEM) offers spatial resolution comparable to XMCD, when combined with a pulsed electron source [1], a temporal resolution comparable to time-resolved MOKE [2]. Whereas MOKE and XMCD are sensitive to magnetization, and are typically used to image the out-of-plane component, LTEM is sensitive to in-plane magnetic fields. With options for in situ sample excitation including optical pulses, alternating currents, and external magnetic fields, LTEM is an ideal platform to probe magnetic dynamics. We present experiments on ferromagnetic nanostructures and skyrmions to illustrate the capabilities.

[1] A Fesit et al., Ultramicroscopy 176, 63 (2017).
[2] NR da Silva et al., arXiv:1710.03307.