Exploring nanomagnetism with soft X-ray microscopy

Abstract

Magnetic soft X-ray microscopy images magnetism in nanoscale systems with a spatial resolution down to 15nm provided by state-of-the-art Fresnel zone plate optics. X-ray magnetic circular dichroism (X-MCD) is used as element-specific magnetic contrast mechanism similar to photoemission electon microscopy (PEEM), however, with volume sensitivity and the ability to record the images in varying applied magnetic fields which allows to study magnetization reversal processes at fundamental length scales. Utilizing a stroboscopic pump-probe scheme one can investigate fast spin dynamics with a time resolution down to 70 ps which gives access to precessional and relaxation phenomena as well as spin torque driven domain wall dynamics in nanoscale systems. Current developments in zone plate optics aim for a spatial resolution towards 10nm and at next generation X-ray sources a time resolution in the fsec regime can be envisioned.Keywords magnetic soft X-ray microscopy, X-ray optics, Fresnel zone plates, magnetic nanostructures, magnetization reversal, fast spin dynamics, X-ray magnetic circular dichroism 3

Domain-wall free energy in Heisenberg ferromagnets

“…This partition function can be rewritten as product of Gaussian integrals by making use of Eqs. (7) and (8):…”

Direct observation of individual Barkhausen avalanches in nucleation-mediated magnetization reversal processes

“…In this letter, we report the findings on the statistical behavior of Barkhausen avalanches for each field step along the hysteresis loop of a CoCrPt alloy film investigated by full-field magnetic transmission soft x-ray microscopy with a spatial resolution of 15 nm. 16 These films exhibit a pronounced PMA and are, therefore, considered as promising candidates for high-density perpendicular magnetic recording media. 17,18 High resolution images of the magnetic domain configuration were recorded at the soft x-ray microscopy beamline 6.1.2 at the Advanced Light Source in Berkeley, CA.…”

“…A detailed description of the experimental setup can be found elsewhere. 16 Magnetic contrast is achieved by the elementspecific effect of x-ray magnetic circular dichroism ͑XMCD͒. The key optical elements are Fresnel zone plates ͑FZPs͒.…”

Observation of Micro-Magnetic Structures by Synchrotron Radiation Photoelectron Emission Microscopy

“…Namely, the element-specific electronic structure of matter can be dynamically observed by SR-based time-resolved spectro-microscopy. In particular, spectro-microscopy combined with the X-ray magnetic circular dichroism effect has been performed at several SR facilities in the world, [99][100][101][102][103][104] and is a suitable technique for observing the domain motion of micro-magnetic structures in the sub-nanosecond range. Ultrafast magnetization dynamics in micron-sized magnetic materials is now one of the important issues relates to the development of fast and high-density data storage devices.…”

“…Some facilities, on the other hand, have made use of time-resolved soft-X-ray microscopy using zone-plate optics, as seen in Ref. 104. In addition, microscopic and spectroscopic observations under a variety of external fields such as magnetic fields, electric fields, and photons, are also indispensable for developing spintronics devices.…”