A review is given of the principles underlying X-ray magnetic circular (XMCD) and linear (XMLD) dichroism spectromicroscopies consisting of polarized X-ray absorption spectroscopy in conjunction with scanning or imaging microscopy. The techniques are shown to have many useful and important capabilities for the study of complex magnetic materials. They offer elemental specificity, chemical specificity and variable depth sensitivity, among others. XMCD microscopy is best suited for the study of ferromagnets and ferrimagnets, and it allows a quantitative determination of the size and direction of spin and orbital moments. XMLD microscopy promises to become a powerful tool for the study of antiferromagnets which are difficult to study by conventional microscopy techniques.
The design of a high resolution photoemission electron microscope ͑PEEM͒ for the study of magnetic materials is described. PEEM is based on imaging the photoemitted ͑secondary͒ electrons from a sample irradiated by x rays. This microscope is permanently installed at the Advanced Light Source at a bending magnet that delivers linearly polarized, and left and right circularly polarized radiation in the soft x-ray range. The microscope can utilize several contrast mechanisms to study the surface and subsurface properties of materials. A wide range of contrast mechanisms can be utilized with this instrument to form topographical, elemental, chemical, magnetic circular and linear dichroism, and polarization contrast high resolution images. The electron optical properties of the microscope are described, and some first results are presented.
We have monitored the progression of the dewetting of a partially brominated polystyrene ͑PBrS͒ thin film on top of a polystyrene ͑PS͒ thin film with scanning transmission x-ray microscopy ͑STXM͒ as well as photoemission electron microscopy ͑PEEM͒. We mapped the projected thickness of each constituent polymer species and the total thickness of the film with STXM, while we determined the surface composition with PEEM. Our data show that the PBrS top layer becomes encapsulated during the later stages of dewetting and that atomic force microscopy topographs cannot be utilized to determine the contact angle between PBrS and PS.
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