Magnetic imaging is important for investigating a variety of systems. For example, the spatial and temporal behavior of magnetization in a solid state spintronic device is crucial for its operation. Some of the most commonly used techniques that provide high spatial and temporal resolution are available at synchrotron X-ray facilities. However, access to such large facilities is not always available, so a laboratory-sized imaging system is desirable.

Schönke et al. describe a new system based on scanning electron microscopy with polarization analysis (SEMPA), which has been around since the 1980s. Only static imaging has been possible to date with their system, but the authors have now developed a method for dynamic imaging. They can achieve a time resolution of a few nanoseconds while retaining the existing nanometer spatial resolution.

The advance reported here uses a special phase-sensitive detection approach that also produces a better signal-to-noise ratio for certain measurements. The new phase-sensitive detection mode demonstrated a signal-to-noise ratio five times larger than normal, which corresponds to a time-saving factor of about twenty-five.

The key advance here combined dynamic SEMPA imaging with the phase-sensitive detection mode. As Daniel Schönke, one of the authors, explained, this required a system with good temporal resolution, which had only been demonstrated recently and only for one other system. State of the art electronics and clever data handling were also both required. Their work used a customized time-to-digital convertor, as well as new software they developed themselves.

The development of dynamic imaging will allow the investigation of nanoscale magnetization dynamics, such as domain wall motion or the switching of nanoscale magnetic bits, in the nanosecond regime.

Source: “Development of a scanning electron microscopy with polarization analysis system for magnetic imaging with ns time resolution and phase-sensitive detection,” by Daniel Schönke, Andreas Oelsner, Pascal Krautscheid, Robert M. Reeve, and Mathias Kläui, Review of Scientific Instruments (2018). The article can be accessed at https://doi.org/10.1063/1.5037528.