We determine the initial growth mode of Co and Fe on Cu (001). In the monolayer range Co and Fe present a clear trend to form clusters on Cu (001). Supposing a perfect epitaxy and fee lattice, the magnetic moment distribution is determined by using a tight binding Hubbard-like Hamiltonian. The influence of the temperature is taken into account in order to compare the theoretical predictions with experimental results.

Spin polarized photoemission is used to study the electronic structure of noble metals deposited on ferromagnetic substrates. Studies of Ag deposited on an Fe (001) substrate reveal a series of minority spin interface or quantum well states with binding energies dependent on the thickness of the silver. Similar behavior is observed for Cu films deposited on a fee Co (001) substrate. Tight-binding Modeling reproduces many of the observations and shows that hybridization of the sp-bands with the noble metal d-bands cannot be ignored.

Here is reported observation of magnetic circular dichroism in both x-ray absorption and core-level photoemission of ultra thin magnetic films using circularly polarized x-rays. Iron films (1–4 ML) grown on a Cu (001) substrate at 150 K and magnetized perpendicular to the surface show dramatic changes in the L2,3 absorption branching ratio for different x-ray polarizations. For linearly-polarized x-rays perpendicular to the magnetic axis of the sample the branching ratio was 0.75. For films ≥ 2 ML, this ratio varied from 0.64 to 0.85 for photon spin parallel and anti-parallel, respectively, to the magnetic axis. This effect was observed either by changing the x-ray helicity for a fixed magnetic axis, or by reversing the magnetic axis for a fixed x-ray helicity. Our observation can be analyzed within a simple one-electron picture, if the raw branching ratios are normalized so that the linear value becomes statistical. Furthermore, warming the films to -300 K eliminated this effect, indicating a loss of magnetization in the film over a temperature range of -30 K. Finally, reversing the relative orientation of the photon spin and the magnetic axis from parallel to anti-parallel allowed measurement with photoemission of the exchange splitting of the Fe 2p and 3p core levels which were found to be 03 eV and 0.2 eV, respectively. These results are consistent with earlier studies, but the use of off-plane circularly-polarized x-rays from a bending magnet monochromator offers -2 orders of magnitude greater intensity than typical spin-polarization measurements. Finally, we have performed preliminary x-ray absorption studies of UFe2, demonstrating the feasibilty of MCD Measurements in 5f as well as 3d Materials.

Magnetic circular x-ray dichroism measurements on CO/Cu and Fe/Cu Multilayers at the K edge of copper show that the 4p -states of copper are significantly spin-polarized by the adjacent magnetic layers. In relation to the phase opposition of the copper thickness-dependent magnetoresistance of CO/Cu and Fe/Cu Multilayers it is of prime importance to notice that the polarization of the conduction electrons of copper follows specifically the polarization of the conduction electrons of the adjacent magnetic element.

We have imaged the magnetic domain structure on the surface of Fe (100) single crystals using energy resolved photoemission microscopy with circularly polarized soft x-rays. The contrast between different domains arises due to Magneto-dichroic effects in the emitted Auger electrons. This new approach offers a surface sensitive way to combine chemical and magnetic information on a microscopic scale.

Circular Dichroic X-ray Photoemission Spectroscopy (CDXPS) experiments have been performed on the 2p core level spectra of polycrystalline Fe film which was magnetized by a low excitation field. The ability to perform the CDXPS experiments in a non remanent mode at a photon energy of 2100 eV opens new and interesting possibilities for the MCD technique in the study of surface and interface Magnetism. Our work on this polycrystalline iron gives some new insights into the understanding of the MCD Mechanism. First results show a similar angular variation for the measured asymmetry, as those observed on a Fe bcc (100) single crystal remanently magnetized in the [100] direction. Our results make clear that the parameters governing the behaviour of the asymmetry factor (A) are not completely described by the relative direction of the Magnetization (M) with the polarization vector of the incident beam (q) and the direction of detection of the photoelectrons (z). The specific outcoming of this work is to clearly show that this behaviour of A is not connected to the crystalline structure of the film for our geometries.

We report on strong magnetic circular dichroism (MCD) in 4f photoemission (PE) from Magnetized Gd(0001)/W(110) films. The shape of the 4f6–7FJ final-state PE Multiplet depends on the relative orientation between photon spin and sample magnetization and can be described within an atomic Model. The spectra rule out antiferromagnetic alignment of the (0001) surface layer and the bulk of Gd. This MCD in 4f-PE from rare-earth materials opens new perspectives in the analysis of surface and thin-film magnetism and as a sensor for circular polarization of soft x-rays.

In the study of thin films and surfaces as well as the examination of superlattices, the careful characterization of these systems including their structural, Magnetic, transport, and other properties has been absolutely crucial to the advancement of the field. As Means of sample preparation have progressed, techniques for evaluating the flatness, continuity, crystallinity, etc. of thin films and surfaces have become ever more necessary to understand the resulting magnetic and electronic properties. Because iron is often a constituent of Magnetic thin films and because the isotope 57Fe shows a strong Mossbauer Effect over a wide temperature range the technique of Mossbauer Spectroscopy offers much to the study of surfaces, thin films, and superlattices.

The role of the final-state character of the emitted electron in Auger electron diffraction (AED) and x-ray photoelectron diffraction (XPD) is examined with respect to magnetic materials. Single scattering cluster calculations with the inclusion of the spherical wave character and the final-state character of the emitted electron (both angular momentum quantum number and magnetic quantum number) show that selective emission from different M-levels, generated by a non-statistical distribution of initial M-levels or by an M-selective excitation process, results in distinctly different emission patterns.

In contrast to Fe(110) -films on W(110), which are magnetized always in the plane as a result of easy-plane magnetic surface anisotropies (MSA), Fe(110) -films on Cr(110) show perpendicular magnetization up to a thickness of roughly 3 Monolayers, as a result of a perpendicular MSA of the Fe(110)/Cr/(110) interface. Acoordingly, Fe(110) -films on W(110), covered with Cr(110), show asymmetric MSA, the easy-plane mSA of the W(110)/Fe(110) -interface opposing the perpendicular one of the Fe(110)/Cr(110) -interface. It turns out that MSA is asymmetric too in Fe(110) films on W(110) covered by Cu, Ag, Au or UHV.

To establish the structural origins of the perpendicular magnetic anisotropy in Co-Pt alloys, a variety of magnetic and structural characterization techniques have been utilized. We have determined that the development of out-of-plane magnetization in these alloys, strongly depends on growth temperature and in contrast to CO/Pt Multilayers, the highest anisotropics and coercivities are observed in polycrystalline alloys with negligible preferred crystallographic orientation. Lattice strain Measurements, surface roughness determination and crystal growth studies indicate that contributions from magnetostrictive and magnetostatic contributions to the perpendicular anisotropy in these alloys are not significant. H RTEM and synchrotron-based x-ray diffraction experiments, on the other hand, confirm the existence of ordered CoPt3 at elevated temperatures. We suggest that the strong temperature dependence of the perpendicular anisotropy is correlated to the onset of spontaneous chemical ordering during the growth which results in anisotropie pair ordering. A tentative model explaining this strong temperature dependence is described.

Magnetic properties of ultrathin Fe and Fe60Au40, alloy films on Au (111) were studied by SQUID Magnetometry and conversion electron Mössbauer spectroscopy. In order to get information on the influence of interdiffusion, iron films with thin alloy zones at the interfaces to Au have been prepared by co-evaporation of iron and gold and compared with iron films with presumably sharp interfaces. It was found that the presence of an 0.5 ML (Mass coverage in Monolayer) alloy zone reduces the effective magnetic interface anisotropy field and affects the growth mode of a subsequently deposited iron film such that the film is more sensitive to annealing. Groundstate Magnetic Moments and hyperfine fields are significantly enhanced in Fe/Au(111) (tFe ≤ 4 ML) and Fe60Au40 films, compared to bulk Fe.

Thin iron carbide films were prepared by introducing iron penta carbonyl (FeCO5) and hydrogen (H2) into a glow discharge. The films are of potential interest in corrosion and wear resistant applications. X-ray diffraction data of films (≈ 7000 Å thick) deposited on glass at 300°C evidenced only Fe7C3. Thinner films were required for examination by analytical and high resolution transmission electron Microscopy. Therefore, two sets of films (“thin” < 200 Å and “thick” ≈ 800 Å) were plasma-deposited on carbon or holey carbon films supported on copper grids. The thin TEM specimens exhibited a fine texture and gave rise to ring diffraction patterns, whereas the thick TEM specimens evidenced two types of structure: (i) half-Micron sized grains separated from one another by 1–2 Microns on the support, although sometimes interconnected by single crystal platelets and (ii) 300 Å grapelike clumps of 100–200 Å crystals, each individually surrounded by a 50 Å non-crystalline coating. The latter structure may result from a post-formation oxidation process which expels carbon from the iron phase into grain boundaries.

MnFe/NiFe exchange structures have been prepared in an ultra-high vacuum sputtering/surface analysis system. Controlled introduction of residual gas impurities such as O2 and H2O at the MnFe/NiFe interface is studied by in-situ x-ray photoelectron spectroscopy (XPS) and the exchange structures are magnetically characterized. Due to the extreme reactivity of the NiFe surface towards O2, the exchange coupling is severely degraded by only small exposures of this molecule to the NiFe surface. In contrast, H2O does not oxidize the NiFe surface and therefore can be tolerated in greater quantities in the sputtering chamber without detrimental loss of exchange. This understanding of the basic surface chemistry of the MnFe and NiFe surfaces can lead to improved sputtering practices in actual manufacturing applications.

The performance of a wide range of modern magnetic thin-film materials for information storage is found to depend dramatically on grain nucleation and coherence at interfaces. Three such systems, Fe/Pt Multilayers, CO/Pt Multilayers, and CoCrTa/Cr bilayers are considered here. High-resolution electron Microscopy (HREM) shows that ordered CoPt and FePt L1o structures can be formed and oriented, using coherence with the substrate, with their magnetically easy c-axes perpendicular to the film plane. This orientation results in the perpendicular magnetization required for Magneto-optic recording Media. Different sputtering gases used in producing CO/Pt Multilayers result in varying degrees of interfacial intermixing, which is shown to strongly affect the perpendicular magnetic anisotropy energy. The required high in-plane coercivity of longitudinal recording media is also correlated with the observed interface coherence and the resulting oriented growth of CoCrTa with the magnetically hard <110> axis perpendicular to the film plane. Many features of the microstructure can be observed directly at the atomic level by HREM, and so the usefulness of this technique is emphasized in this paper.

The room-temperature growth of Fe on Cu(100) has been studied using the scanning tunneling Microscope (STM) to determine low-coverage growth mode and local structures related to the FCC-BCC structural transformation. Results for submonolayer deposition demonstrate an initial interchange of deposited Fe atoms with substrate Cu. This leads to a highly rough Fe-Cu interface and growth characteristics that for different experimental techniques can resemble 3-D island growth or layer-by-layer growth. For a thickness ∼14 Monolayers, the FCC-BCC transition is observed to occur via the formation of fairly large martensitic grains, rather than by a change in atomic aggregation. The implications of the instability of FCC-Fe, as evident in both low- and high-coverage data, are considered.

We have developed a novel, high-resolution magnetic imaging technique, scanning-ion microscopy with polarization analysis (SIMPA). In SIMPA, a highly-focused, scanning Ga+ ion beam is used to excite spin-polarized electrons at surfaces of ferromagnetic Materials. By Measuring the intensity and the spin polarization of the emitted electrons using a newly developed, compact mott polarimeter, topographic and magnetic images of magnetic structures are obtained. We report on first SIMPA studies on single-crystalline Fe samples.

We investigated structural and magnetic properties of Fe/Zr Multilayer films using high-resolution transmission electron Microscopy, X-ray diffraction and vibrating sample Magnetometry. For films with wavelength (Λ) ≥ 80Å, the interface region between the Fe and Zr layers exhibits a 15–20Å thick amorphous structure. The Magnetization curves of these films showed a monotonous decrease in the saturation magnetizations with Λ, whose trend is well explained by a simple asymptotic model that assumes the interface amorphous layer to be non-ferromagnetic. Films with Λ≤40Å exhibit a compositionally-Modulated amorphous structure. The latter films are paramagnetic except for the one with Λ=40Å, which showed a superparamagnetic behavior.

We have studied the influence of ultra-thin interfacial Fe layers on the structural and magnetoresistance properties of CO/Cu Multilayers. Our results show that the giant magnetoresistance arises from spin dependent scattering at the CO/Cu interfaces and in the bulk of Co, the interfacial contribution being predominant. We also demonstrate that the close-packed crystallographic structure of Co and Cu is very sensitive to the insertion of interfacial bec Fe layers: for small thicknesses, Co as well as Cu adopt a metastable bec structure.

The resistance and magnetoresistance of Gd/W Multilayers have been measured at temperatures between 300K and 4K and in fields of up to 7 Tesla. The temperature coefficent of resistance is strongly influenced by the thickness of the Gd layers, becoming negative at a Gd layer thickness of 0.8nm. The Magnetoresistance is dominated by the Gd below about 100K. Multilayers which show reduced saturation magnetisation at 4K also have an unusual form of magnetoresistance around 100K. We suggest that this may be due to antiferromagnetic alignment of the Gd and W Moments at low applied fields.