Element-Selective Magnetic Imaging in Exchange-Coupled Systems by Magnetic Photoemission Microscopy

Abstract

We have used a photoemission microscope to obtain element-resolved magnetic contrast in stacked magnetic thin film systems. Magnetic information is thereby provided by X-ray magnetic circular dichroism. Elemental sensitivity, which is crucial for studying magnetic coupling phenomena in systems with several different layers, is achieved by tuning the energy of the illuminating photons to atomic absorption edges. We present measurements of a Ni-coated Co micropattern on Cu(001), and a wedged Co/Cr/Fe(001) sample. In the former sample the Ni magnetization is seen to follow the magnetization of the Co pattern, thereby changing from an out-of-plane easy axis in areas without underlying Co to in-plane on top of the Co microstructures. In the latter a reversal of the exchange coupling of the Co layer to the Fe magnetization is observed when the Cr layer thickness exceeds approximately two monolayers. A small net magnetic moment is also observed in the Cr spacer layer, which follows in sign the Co magnetization at the reversal of the exchange coupling. This finding is discussed in terms of interface roughness or interdiffusion.

Application of Synchrotron Radiation Techniques for Model Validation of Advanced Structural Materials

“…Photoemission Electron Microscopy/X-Ray Magnetic Circular Dichroism (PEEM/XMCD) X-ray PEEM is a synchrotron-based soft X-ray microscopy technique which was first developed in the 1930s and has since become a well-established imaging technique [6][7][8] . This technique uses the secondary electrons emitted from a sample surface upon absorption of photons to obtain a magnified image of a material.…”

Physics of Low Dimensional Systems

“…Except for the trivial case of a nOll-magnetic top layer none of the various other imaging techniques is capable to reveal thr magnetic structure of a 43 ) buried layer. TXM could work in principle if the layered structure is sufficiently thin and the X-ray optics allows tunability over a photon energy range comprising the relevant absorption edges.…”

“…In the following we will present a typical example in order to illustrate the performance of the PEEM technique. Kuch et al 43 have investigated the sandwich structure of a Co film being separated from an Fe substrate by a Cr-wedge for deposition at 500 K. Figure 7 shows a result obtained by the XMCD-PEEM technique. The sample was prepared in the following way: The Cr-wedge with increasing thickness from 0-3 monolayers (ML) was grown on a Fe(lOO)-whisker (single crystal) surface.…”

X-ray Magnetic Circular Dichroism for Quantitative Element-Resolved Magnetic Microscopy

“…Since then quite a number of studies have been performed by either electron-optic imaging of the photoemitted electrons in a photoelectron emission microscope (PEEM) [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] or by X-ray imaging in an X-ray microscope [24][25][26][27][28]. Taking advantage of the element-selectivity, magnetic imaging using XMCD as contrast mechanism offers the unique possibility to obtain layer-resolved domain images of magnetic multilayered samples, if different elements are used in different magnetic layers.…”