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 2 p3p3p 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. ͓S0163-1829͑97͒09537-4͔

We investigate the magnetic properties of Mn adsorbates on Fe͑100͒ 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 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 B at 120 K. The magnetic signal vanishes near 1 ML coverage, consistent with the theoretically predicted c(2ϫ2) antiferromagnetic ground state of the monolayer.

Ultrathin films of NiO grown on Ag͑100͒ 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 ͑microspectroscopy͒. These changes indicate the presence of antiferromagnetic domains which can be distinguished because the magnetic moments ͑or components thereof͒ are either collinear or perpendicular to the electric field vector of the linearly polarized light.

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. PACS numbers: 78.20.Ls, 75.60.Ch, 78.70.Dm Spectroscopy of the core levels of the ferromagnetic transition elements has shown in recent years to be surprisingly rich in features caused by the Coulomb and exchange interactions between the core hole and the spinpolarized valence electrons. X-ray absorption experiments (XAS) with linearly polarized light [1] show a change of the spectra when the polarization vector is either parallel or perpendicular to the magnetization axis, according to the selection rules Am = 0 or Am =~1 , respectively. Magnetic circular dichroism (MCD) in x-ray absorption [2,3]can be understood as a spin-dependent excitation of core electrons into empty states above the Fermi level, whichbecause of the ferromagnetism are spin polarized [4].The spin dependence in the excitation arises from coupling between light helicity and the orbital momentum of the excited electron, which is in turn coupled to the spin of the photoexcited electron by spin-orbit interaction. Sum rules, which allow one to extract quantitatively spin and orbital moments, make MCD in absorption a very attractive technique [5]. By measuring the photoabsorption cross section via the total photoelectron yield of the sample, it is even possible to obtain spatially resolved and chemically specific magnetic information [6].In photoemission, even though the final state of the photoelectron far above the Fermi level has only negligible exchange and spin-orbit interactions, related effects can also be observed. It is well known that core level photoelectrons from ferromagnets in general carry a spin polarization due to exchange [7]. Apart from magnetic circular and "conventional" (as described above for XAS) linear dichroisrn, a new type of magnetic linear dichroism was recently reported for photoemission appearing on magnetization reversal [8]. This effect requires that the vectors of magnetization, electric radiation field, and electron emission form a chiral system with the angle between light polarization and electron emission different from 90, and occurs only in angle-resolved experiments. In photoabsorption, the angular acceptance of the excited electrons is not restricted, so that it is, in principle, an angle-integrating experiment. However, Kao and co-workers [9] reported in 1990 for photon energies near the Fe 2p excitation thresholds a change of the refIectivity for obliquely incident p-polarized light when the magnetization is switched between th...

We have studied the transverse magneto-optical Kerr effect of a Fe͓͑5.7% Si͒001͔ sample and of ultrathin films of Fe evaporated onto Ag͑001͒ 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. ͓S0163-1829͑97͒01822-5͔Magneto-optical effects are used in the visible part of the spectrum for magnetic domain imaging. The most important ones are the polar and the longitudinal Kerr effects which affect the polarization of the reflected light beam. Less frequently used is the transverse magneto-optic Kerr effect which refers to the dependence of the reflected intensity on the sense of the magnetization in the transverse scattering geometry, i.e., when the magnetization is directed perpendicular to the scattering plane. In a continuum view of the magnetic medium, these effects are related to the finite offdiagonal elements of the dielectric tensor. 1 To first order these depend linearly on the magnetization (M ). In the visible part of the spectrum the transverse magneto-optical effect is very small and hence the polar and the longitudinal Kerr effects which give a strong magnetic contrast using the crossed-polarizer technique are used. It was shown recently that at core level thresholds the magneto-optical effects are very strong. This was shown first for the Fe 2 p level 2-4 and subsequently for the Co 3 p level. 5 Highly efficient and tunable analyzers are not yet available for the soft-x-ray regime to accomplish domain imaging using the longitudinal or polar Kerr effect. However, it appears to be feasible to extend the concept of element-specific imaging using a scanningtype microscope with tunable primary photon energies 6,7 towards element-specific imaging of magnetic domains by exploiting the huge transverse magneto-optical Kerr effect ͑T-MOKE͒ at the core level thresholds. The relation between the compositional distribution and the magnetization of more complex materials which are used, e.g., in magneto-optical storage and modern permanent magnets can thereby be investigated. The surface sensitivity can be altered in principle by varying the angle of incidence. The 3p core levels of the transition metals are at binding energies of about 50 eV and the reflectivity at about 15°grazing incidence angle is large enough to accomplish also magnetic domain imaging when an intense soft-x-ray beam is available as, e.g., from synchrotron radiation facilities equipped with undulator beam lines. At the 2p binding energies sizable reflectivity is only obtained at incidence angles very close to grazing, which makes imaging in reflection very difficult. The existence of the transverse MOKE implies a sizable dichroism in the total photoyield. This kind of magnetic dichroism has been used