Ultrathin films of NiO grown on Ag(100) were investigated by photoemission microscopy. To image antiferromagnetic domains, linearly polarized light from an insertion device was used. The micrographs revealed lateral changes of the spectral line shapes of the 3p photoemission spectrum which were confirmed by taking full spectra with a lateral resolution of 150 nm (microspectroscopy). These changes indicate the presence of antiferromagnetic domains which can be distinguished because the magnetic moments (or components thereof) are either collinear or perpendicular to the electric field vector of the linearly polarized light.

The Fe L3M2,3M2,3 Auger spectrum measured with the light helicity vector perpendicular to the magnetization direction shows a strong magnetic circular dichroism (MCD). Such an effect is not expected in a two-step model when the photoelectron is excited into a non-interacting continuum state and appears to be absent in strongly correlated materials, such as nickel. We tentatively explain this phenomenon by a spin-dependent screening of the intermediate core-hole state. Supporting evidence for a breakdown of the independent-particle model for iron is found in the observed MCD of the Fe 2p photoemission.

We have studied the transverse magneto-optical Kerr effect of a Fe[(5.7% Si)001] sample and of ultrathin films of Fe evaporated onto Ag(001) in the soft-x-ray regime at the 3p core level threshold of Fe. We test the relationship between the asymmetries in the reflectivity and in the total photoyield which have been measured simultaneously.

The Fe 2p photoemission of ferromagnetic iron shows a dichroism which indicates a strong difference in hybridization for spin-up and spin-down electrons. In contrast, the dichroism of the localized Mn surface alloys reveals intense unscreened satellite structure. The spin polarization of the core hole is quantified using the dichroism in the Fe L3M2,3M2,3 Auger spectrum measured with the light helicity vector perpendicular to the magnetization direction. The observations in the 3d metals are in strong contradiction with the expectations from an independent-particle model.

We investigate the magnetic properties of Mn adsorbates on Fe(100) in the regime up to a few monolayers. Magnetic circular dichroism in absorption shows long-range ferromagnetic order for the Mn adsorbate, with antiferromagnetic alignment with respect to the Fe substrate. Element-specific magnetic domain imaging and hysteresis measurements show that the macroscopic magnetic behavior of the Mn adlayer is fully determined by the Fe substrate. For coverages below 0.5 ML the Mn absorption spectra show rich structures that are typical for localized d states. From this the Mn ground state is identified as a mixture of atomiclike d(5) and d(6) states, with a local spin moment of 4.5 mu(B). However, the circular dichroism is 2.4 times smaller than expected for this ground state, suggesting disorder within the Mn adsorbate with an ordered moment of 1.9 mu(B) B at 120 K. The magnetic signal vanishes near 1 ML coverage. consistent with the theoretically predicted c(2X2) antiferromagnetic ground state of the monolayer.

We studied the electronic and magnetic properties of ultrathin Mn films deposited onto Cu, Ni, and Fe surfaces with x-ray-absorption and resonant-photoemission spectroscopies. The observed strong changes in the Mn $2p$ branching ratio as a function of coverage and substrate type indicate a change from localized to itinerant behavior. The $2p3p3p$ resonant photoemission triplet state shows two features which can be assigned to a well-screened and a poorly screened final state. The intensity ratio between these two states allows corroboration of the electron localization. Magnetic circular x-ray dichroism gives the spin magnetic moment of the Mn ground state and information about the Mn-substrate magnetic coupling. Combining these results we propose a simple explanation for the magnetic behavior of the Mn layers.

Imaging of ferromagnetic domains by photoemission microscopy based on magnetic dichroism in the total yield is illustrated by various examples. By using different light polarizations, different components of the magnetization near to the surface can be revealed without movement of the sample. Examples include bulk crystals, ferromagnetic alloys, ultrathin films and submonolayer adsorbates. First results of a time-resolved study under an external magnetic field are presented.

We have studied the electronic and magnetic structure of ultrathin Mn films grown on 3d transition metal surfaces using X-ray absorption and resonant photoemission. At submonolayer coverages Mn deposition leads to a highly localized 3d5-like ground state. A delocalized metallic ground state is formed upon increasing MnMn 3d orbital overlap after percolation of the film. A similar state can also be formed through hybridization between Mn and substrate 3d states even at very low coverages. As shown by magnetic circular dichroism Mn exhibits long-range ferromagnetic order only in the latter systems, which evidences the importance of 3d hybridization for exchange coupling.

We investigate the magnetic properties of Mn adsorbates on Fe(100) in the regime up to 0.5 monolayers. Magnetic circular dichroism (MCD) in absorption shows long-range ferromagnetic order for the Mn adsorbate, with antiferromagnetic alignment with respect to the Fe substrate. Element-specific magnetic-domain imaging shows that the macroscopic magnetic behaviour of the Mn adlayer is fully determined by the Fe substrate.

Among the techniques for studying magnetic materials, methods utilizing magnetic dichroism in the soft x-ray region are receiving particular attention because of the unique feature of chemical specificity introduced by probing core levels. In soft x-ray absorption of linearly polarized light, the dichroism is proportional to the square of the magnetization M. The transverse magneto-optic Kerr effect is characterized by a change of the specular reflectivity when M is reversed, thus it is linear in M. Due to the relationship between reflected and transmitted radiation, a dichroism may also be expected in the absorption. We confirmed this by quasi-simultaneous measurement of the reflectivity and total yield around the Fe and Co 3p thresholds, using p-polarized light at oblique incidence: Switching the magnetization between the two directions normal on the plane of incidence indeed shows a magnetic dichroism. The relationship between the dichroisms in total yield and specular reflectivity was investigated as function of incidence angle. In addition to this new form of magnetic dichroism, other forms have been explored for imaging near-surface magnetic domains of elemental and compound materials in a total yield microscope. By using different light polarizations different components of the magnetization are detected. p- and circular polarization yield magnetization components parallel to the surface, normal to and in the plane of light incidence, respectively. With linearly s-polarized light, images similar to those with circularly polarized light were obtained. This is evidence for a sizeable Faraday rotation, leading to a significant degree of circular polarization before the optical transition takes place. The helicity of the Faraday-induced ellipitical polarization depends on the local sample magnetization, thereby generating the magnetic contrast in an analogous fashion as does circularly polarized light. This mechanism is expected and found to be effective also for p-polarized light, however, with contrast smaller than that related to the transverse MOKE. Finally, we report first results for an antiferromagnet, where domains were observed via the M-quadratic Voigt effect in the soft x-ray region.

We have found a new type of magnetic linear dichroism in photoyield spectra at the Fe and Co M2,3 edges. Spectra excited by p-polarized light at oblique incidence show cross section dependence on the sign of the magnetization. The experimental geometry is the same as that of the transverse magneto-optic Kerr effect (T-MOKE). The dichroism is enhanced when the light impinges on the sample towards grazing incidence. The T-MOKE at the Co M edge also measured simultaneously. The new type of dichroism can be applied for imaging of magnetic domains of surfaces by a photoelectron microscopy.

The discovery of magnetic dichroism in core level spectroscopy opened the route to magnetic domain imaging. By employing light in the soft X-ray regime one obtains chemically specific information. Besides the commonly used circular magnetic dichroism (MCD), we demonstrate feasibility of using linear magnetic dichroism in absorption for domain imaging in the photo electron emission microscope (PEEM). By combining different light polarizations, one obtains vectorial information on the magnetic moment distribution close to the surrface.

We report a dependence of the photoabsorption cross section as measured by total electron yield at the Fe and Co 3p thresholds on the sign of the magnetization for p-polarized light at oblique incidence. Peak-to-peak asymmetries up to 4% are observed. The asymmetry increases towards grazing incidence, where the total sample current is smallest. The transverse magneto-optic Kerr effect measured simultaneously shows a peak-to-peak asymmetry of up to 23% at the Co 3p threshold. The dichroism is used to image magnetic domains on an Fe(100) surface in a photoelectron emission microscope.

We have found a new type of magnetic linear dichroism in photoabsorption spectra at the Fe M2,3 edge. The spectra excited by p-polarized light at oblique incidence show dichroism when the magnetization direction changes from parallel to antiparallel to n × q, where n is a vector perpendicular to the sample surface and q is the photon momentum. The dichroism is enhanced when the light impinges on the sample towards grazing incidence.