The magnetic linear dichroism (MLDAD) in Fe 2p photoemission spectra of an epitaxial ultrathin iron film has been determined. The experiment reveals multiplet related spectra, which allow a detailed characterization of the photoemission process in a simple final state model, that emphasizes the core-valence interaction in Fe 2p photoemission. The same model was used to describe the Cr 2p photoemission spectrum of Cr adsorbates on a Fe surface. The importance of the investigations for the discussion of the 2p photoelectron spectra of 3d metals is pointed out.

Giant magnetoimpedance (GMI) describes the strong dependence of the impedance of soft magnetic microwires or thin film systems on the presence of a small external magnetic field. The change of the impedance can be in the order of several hundred percent. Numerous applications have been proposed or are employed, e. g. the measurement of extremely low magnetic fields. As thin film structures are better suited for assembly and integration than wires, we have focused on the development and characterization of thin film structures. The sensors consist of FeCuNbSiB/Cu/FeCuNbSiB thin film trilayer systems. In these structures, the difference between the longitudinal and the transversal and polar MI-effects is very large as compared to GMI-wires. We discuss different approaches to measure the GMI and we show that small amounts of superparamagnetic particles can be detected.

We describe concept, design, and performance of a novel spin polarimeter based on spin-dependent specular reflection of electrons from a Fe(100) surface. The Fe surface is prepared as an ultrathin film on Ag(100). By tuning the energy of the electrons to a critical point in the Fe band structure, a large spin asymmetry combined with a large scattering efficiency is achieved. The polarimeter yields a figure of merit up to 10−2 for the best Fe(100) surfaces.

Antiferromagnetic domains at surfaces of NiO single crystals were studied by polarization dependent soft X-ray absorption at the Ni2p absorption edges. Spatially resolved information is obtained by monitoring the absorption via the total yield of electrons in a photoemission electron microscope. On the (100) surface, stripe shaped domains are found with widths of the order of a few 10 μm, extending over 100s of μm. The polarization dependence shows a sign change of the contrast for every 90° of rotation, as expected for the antiferromagnetic twin domains with the major portion of the antiferromagnetic axis within the plane of the surface. The domains are not affected by surface topography. This suggests that the formation of domains is governed by defects in the bulk, which lead to nucleation of domains at specific sites.

The orientation of magnetic moments at the (100) surface of antiferromagnetic NiO single crystals is studied by x-ray linear magnetic dichroism in photoemission microscopy. T domains are observed terminating at the surface, with domain boundaries running mostly along in-plane [10] directions. From the detailed polarization dependence we find that the magnetic surface structure of a cleaved crystal is bulk terminated. This is in contrast to sputtered surfaces, where magnetic moments lie within the surface plane, forming a magnetically relaxed structure. These findings are of importance for understanding the exchange bias phenomenon.

Antiferromagnetic domains at the NiO(100) single-crystal surface are imaged by photoemission microscopy excited by linearly polarized near UV radiation from a mercury vapour light source. The contrast is observed by subtracting images excited by s- and p-polarized light. This contrast is compared with the contrast from X-ray magnetic linear dichroism (XMLD). Here the XMLD contrast is gained by subtracting two images excited by the same polarization but different photon energies at the Ni2p core excitation. (C) 2001 Elsevier Science BY. All rights reserved.

Antiferromagnetic domains at the NiO(100) single-crystal surface are imaged by photoemission microscopy excited by linearly polarized near UV radiation from a mercury vapour light source. The contrast is observed by subtracting images excited by s- and p-polarized light. This contrast is compared with the contrast from X-ray magnetic linear dichroism (XMLD). Here the XMLD contrast is gained by subtracting two images excited by the same polarization but different photon energies at the Ni2p core excitation.

The linear dichroism in the 2p photoelectron spectra of free Cr atoms and Cr atoms bound to an Fe surface has been determined. The spectra of free laser-oriented atoms are compared to Hartree-Fock calculations and the corresponding spectra of magnetized surface layers. The importance of satellites and of the 2p-3d Coulomb interaction in the final ionic state is demonstrated in both cases.

The transverse magneto-optical Kerr effect (T-MOKE) was investigated for thin epitaxial films of Fe grown on Ag(100) in the region of the 2p excitation threshold. The experimental reflectivity and asymmetry spectra are compared to those derived from the complex dielectric function tensor. The T-MOKE asymmetry is a mixture of both the real and imaginary parts of the off-diagonal elements of the dielectric function tensor, depending sensitively on the relative magnitudes between the real and imaginary parts of the diagonal elements. We demonstrate the possibility to determine the exchange coupling between a ferromagnetic thin film and an adsorbed monolayer by T-MOKE. (C) 1999 American Institute of Physics. [S0021-8979(99)64308-0].

Electron-exchange processes in dipole-forbidden $d\ensuremath{-}d$ excitations of the $3d$ transition-metal oxides NiO, CoO, and MnO have been investigated by spin-polarized electron-energy-loss spectroscopy over a wide primary energy range and for different scattering geometries. At primary energies corresponding to certain excitation thresholds, the $d\ensuremath{-}d$ excitations in CoO and MnO show resonant enhancement, similar to the resonances previously found for NiO. The resonance around 38 eV, which is assigned to simultaneous excitations within the $d$-multiplet and oxygen excitations, occurs at nearly identical primary energy, due to identical energetic positions of the oxygen levels in the three oxides. The metal $3s\ensuremath{-}3d$ resonance is shifted toward lower energy in CoO and MnO, according to the lower binding energies of the $3s$ levels. In resonance, the $d\ensuremath{-}d$ excitations are highly exchange dominated. Off resonance, a strong superposition with direct dipole-scattering processes has been found for the dominant multiplicity-conserving transitions in NiO and CoO. Excitation by direct dipole scattering is completely missing in the spin-forbidden, multiplicity-changing transitions in MnO.

Electron-exchange processes in excitations within the d-multiplet of the TM-ions in NiO〈100〉 and CoO〈100〉 had been examined by spin-polarized electron energy-loss spectroscopy. The excitations at surface and bulk ions in NiO show a completely different scattering geometry dependence, providing the possibility of distinguishing between both. In addition to the well-known 0.6 eV surface state, the loss-structure at 2.1 eV excitation energy was identified as surface excitation. In CoO, no surface d-d transitions have been found. Different spin-flip intensities in the excitations of the bulk Co-ions had been used to identify multiplicity changing and conserving transitions definitely. By use of the previously found resonance primary energies and suitable scattering geometries, new d-d excitations had been measured in NiO as well as in CoO.

Electron exchange processes in d-d transitions of the Ni2+-surface ions in NiO(100) had been examined by ''complete'' spin-polarized electron-energy-loss spectroscopy. Surface and bulk excitations show a completely different scattering geometry dependence, providing the possibility to distinguish between them. Besides the well-known 0.6 eV surface state, the loss structure at 2.1 eV excitation energy was identified as surface excitation. By use of the resonance primary energies, a new excitation at 1.3 eV was found, which was assigned to the B-3(1)-->(3)A(2) surface excitation.