A full-field transmission x-ray microscope for time-resolved imaging of magnetic nanostructures

Abstract

Abstract. Sub-nanosecond magnetization dynamics of small permalloy (Ni 80 Fe 20 ) elements has been investigated with a new full-field transmission microscope at the soft X-ray beamline P04 of the high brilliance synchrotron radiation source PETRA III. The soft X-ray microscope generates a flat-top illumination field of 20 μm diameter using a grating condenser. A tilted nanostructured magnetic sample can be excited by a picosecond electric current pulse via a coplanar waveguide. The transmitted light of the sample plane is directly imaged by a micro zone plate with < 65 nm resolution onto a 2D gateable Xray detector to select one particular bunch in the storage ring that probes the time evolution of the dynamic information successively via XMCD spectromicroscopy in a pump-probe scheme. In the experiments it was possible to generate a homogeneously magnetized state in patterned magnetic layers by a strong magnetic Oersted field pulse of 200 ps duration and directly observe the recovery to the initial flux-closure vortex patterns.

Magnetic imaging with polarized soft x-rays

“…the probing xray pulses to the excitation pump pulse of the sample and then record images at variable delay time between the electronic pump and the x-ray probe. At the ALS, where most of the presented timeresolved magnetic x-ray imaging studies featured in this article were obtained this approach is mostly performed in the so-called 2-bunch mode of the storage ring, although gated CCDs have demonstrated the ability to select individual bunches from the regular multibunch operation of synchrotrons [49]. At the ALS, the x-ray pulse length that sets the temporal resolution is about 70 ps.…”

Time-resolved imaging of magnetic vortex dynamics using holography with extended reference autocorrelation by linear differential operator

“…In case of thin film patterned magnetic elements, such as microscopic permalloy (Py, Ni 81 Fe 19 ) squares or dots, the focus of research has been covering a number of topics including the understanding of the eigen-modes of gyration in single elements11112151617, coupled oscillations in assemblies or patterns of elements18192021222324, non-linear effects24252627, manipulation of core dynamics11121315 and their practical application781213. In many cases the investigations have been based on time-resolved imaging using optical28293031 or x-ray techniques1732333435. The spatial resolution in the best case is limited to the wavelength of the optical probe convoluted with the specifics of the particular techniques and their limitations.…”