Abstract We report on the fabrication and transport properties of magnetic multilayers with widths down to 100 nm. We employ e-beam processed nano-deposition masks to pattern magnetic multilayers which define nano-wires by lift-off or by a removal process such as ion-milling. Two different magnetic multilayer systems (antiferromagnetically coupled Co/Cu multilayers and NiFe/Cu/Co spin-valves) are investigated. Structures resulting from the lift-off process show high contact resistance and high resistivities while ion-milled structures show resistivities close to that of bulk. For Fe(50Å)/[Co(15Å)/Cu(20Å)]x20 /Cu(30Å), patterned nano-wire structures display no negative magnetoresistance but a positive magnetoresistance that is linear with applied field and no apparent hysteresis. For Ta(50Å)/NiFe(50Å)/Cu(35Å)/Co(20Å)/Cu(30Å), we found the resistance to decrease as the absolute value of magnetic field is decreased and found hysteresis to be present.

Different phases of FeN thin films and Fe/FeN multilayers were prepared by reactive rf sputtering. The release of nitrogen and the crystallographic transformations during annealing were monitored by thermal desorption spectrometry and X-ray diffraction experiments. Finally, the diffusivity of nitrogen in the γ-Fe4N phase was evaluated.

Most soft x-ray magnetic dichroism studies are carried out with light of mixed polarization. The effect of incomplete circular polarization is usually taken care off by linearly extrapolating the data to Pcirc=l. Using a classical model which includes the polarization factor we show that the MCD-effect, which is the normalized quantity 2(I+-I-)/(I++I-), is highly non-linear with regard to cire. With a specially designed quadruple reflection phase shifter we measured the MCD effect with Pcire<l as well as with Pcirc∼1. MCD spectra of Fe around the M2,3 transition verify our model calculations of the polarization dependence. The data indicate that the observed non-linear response of the MCD-effect to Pcirc can generally introduce large errors in the quantitative analysis of MCD data where spin <Sz> and orbital <LZ> moments are extracted by means of sum rules.

The effect of in-plane strain on the magnetic anisotropy of [110]-oriented epitaxial TbFe2 films was studied. DC magnetron cosputtering was used to grow epitaxial TbFe2(110) films on A12O3(1120) substrates with an epitaxial Nb(110) buffer layer. Torque magnetometry showed that the films had uniaxial anisotropy, and the torque curves were used to determine the magnetic anisotropy constants of the films by analyzing the rotational hysteresis loss. Film strain was measured using synchrotron radiation. The film strain and anisotropy measurements confirm that the uniaxial anisotropy results from tensile strain in the TbFe2(110) films. This agrees with theoretical calculations of magnetic anisotropy which show that tensile strains can induce a uniaxial anisotropy in TbFe2(110) films.

[Cu(20Å)/NiFe(7Å)/Ni(6Å)/NiFe(7Å)]10Cu(50Å) multilayers were deposited on 4 ° tilt-cut Si(lll) using 3-gun rf magnetron sputtering system. An in-plane uniaxial magnetic anisotropy was found and the uniaxial magnetic anisotropy constant was about 3×104 erg/cm3. The multilayers on non tilt-cut Si(lll) with Cu underlayer did not show any anisotropy. The crystal structure of the multilayer on 4 ° tilt-cut Si(111) was studied using TEM work and the magnetic anisotropy is originated from the growth of (110) preferred orientation of the multilayer. When other material such as Ni or NiFe was used as an underlayer for the multilayer, the magnetic anisotropy disappeared and the crystal structure was (111). The multilayer without underlayer did not show any magnetic anisotropy either. It is thought that Cu underlayer was grown with (110) orientation on 4 ° tilt-cut Si(111) through the ledges in Si wafer and worked as a template for the growth of the multilayer.

Magnetic X-Ray resonant scattering performed at the Dysprosium Lni absorption edge permits to study the magnetic behaviour of a 3000 Å thick Dy film. The development of an helical magnetic order gives rise to intense magnetic resonant harmonics. The energy dependence of the resonant intensity has been investigated and presents a double resonance at the second harmonic measured in the σ-π geometry. The accurate thermal variation of the turn angle and of the c-parameter is given. These evolutions reveal the stabilisation of the helical phase in the Dysprosium film compared to the bulk case.

The photothermally modulated ferromagnetic resonance (PM-FMR) has been successfully applied to investigate the position dependence of FMR properties of wedged Fe-samples. The temperature dependence of the surface contribution to the anisotropy could be separated from the demagnetizing field with high accuracy. The oscillating first order interlayer exchange coupling and the anisotropy fields of the Fe-films of a Fe/Cr-wedge/Fe-sample (3.0/0.7–2.8/2.0 nm) were deduced from PM-FMR spectra.

Thin films of Ni and Co have been investigated by Brillouin Light Scattering (BLS). The samples, grown by evaporation (Ni) and RF sputtering (Co) on silicon substrates, have thicknesses in the range 16–98 nm. The Damon-Eshbach surface mode and several bulk standing waves have been detected. A macroscopic approach has been adopted in order to calculate the dispersion relations of the spin waves. The method takes into account the dipolar and exchange interactions, together with bulk and surface magnetic anisotropies. The spin waves frequencies and the scattering cross section have been calculated by using the bulk and surface anisotropies as relevant fitting parameters.

The microstructure of Co90Feio/Ag giant magnetoresistive multilayer films has been investigated using x-ray diffraction (XRD) and cross-sectional transmission electron microscopy. Columnar grains with a (111) fiber growth texture is observed. A comparison is made between the observed layering structure and earlier multilayer schematics based on the literature and magnetic and magnetoresistive measurements as a function of layer thickness. A direct correlation is made between superlattice satellite peak signals from selected area electron diffraction patterns and XRD scans.

The magnetic properties of granular CO25Cu75/CU multilayer films prepared by sputtering onto heated glass substrates have been investigated in the range of ultrathin alloy films (5–250Á) and Cu spacer thicknesses (0–50Å). Both the coercive field at 10K and the maximum superparamagnetic blocking temperature TB are found to be sensitive to finite-size effects in single-layer films, and to interactions between layers in multilayer films. Our results indicate that the magnetic properties of granular alloy layers can be engineered to a large extent by selectively modifying the local environment of the Co particles.

Metallic Multilayers (MLs) have attracted a considerable interest during these last years because of their unusual properties. In small periods ML's (a few nm) the high density of interfaces give rise to structures very far from equilibrium. Au/Ni multilayers have been grown in the (111) orientation by M.B.E. on Si(100) via a Cu(100) buffer layer. Two different parameters have been studied: the Au:Ni ratio at constant (4 nm) superperiod and the superperiod at constant (1:1) Au:Ni ratio. The full strain state of Au and of Ni has been determined via x-ray diffraction measurements. The high lattice parameter misfit beween Au and Ni (14%) implies that all the layers are partially relaxed. Residual strains as high as several % are encountered. The residual strain in the Au layers is clearly correlated with their thickness. A residual stress as high as 3.9 GPa is determined in the thinner layers.

We report on the study of MCD in resonant PE, using Gd metal as an example. When the photon energy is changed across the Gd 4d → 4ƒ excitation region, the PE-MCD spectrum varies substantially. Based on atomic-multiplet theory, we present a consistent picture of MCD in resonant 4d → 4ƒ PE and x-ray absorption at the 4d-edge, where all spectral changes can be explained by the angular-momentum of the intermediate absorption state. The present analysis shows: when tuning to a specific line of the 4d x-ray absorption spectrum with a total angular momentum J', only the associate multiplet component is found to resonate. At the ‘giant resonance’, the shape of the MCD-PE signal closely resembles the off-resonance case; this finding is explained within atomic-multiplet theory allowing a straightforward use of MCD in 4d-resonant PE (i) for element-specific analysis of multicomponent magnetic systems with high surface sensitivity and (ii) for surface-domain imaging by PE microscopy.

Submonolayer films of Mn grown on fcc Co(001) are ferromagnetically ordered with the magnetization direction oriented parallel to the Co substrate magnetization. After exposure to oxygen the Mn atoms remain ferromagnetically ordered but their magnetization direction rotates 180 degrees and is now aligned antiparallel to the Co magnetization. This behavior in magnetic coupling between the Mn and Co films is not consistent with recent theoretical predictions.

Photoelectron emission microscopy (PEEM) has proven to be a versatile analytical technique in surface science. When operated with circularly polarized light in the soft x-ray regime, however, photoemission microscopy offers a unique combination of magnetic and chemical information. Exploiting the high brilliance and circular polarization available at a helical undulator beamline, the lateral resolution in the imaging of magnetic domain structures may be pushed well into the sub-micrometer range. Using a newly designed photoemission microscope we show that under these circumstances not only domains, but also domain walls can be selectively investigated. The high sensitivity of the technique yields a sizable magnetic contrast even from magnetic films as thin as a fraction of a single monolayer. The combination of chemical selectivity and information depth is successfully employed to investigate the magnetic behavior of buried layers and covered surfaces. This approach offers a convenient access to magnetic coupling phenomena in magnetic sandwiches.

In this paper, the interrelation between structural and magnetic properties of ultra-thin Mn films epitaxially grown on (001) bcc Fe is studied. The Mn growth and in-plane structure were controlled by electron diffraction (RHEED). The structures of the Mn films were determined by using X-Ray absorption spectroscopy (SEXAFS). Finally, the magnetic properties were studied by using X-Ray magnetic circular dichroïsm (XMCD). All the experiments were performed under ultra-high vacuum. As shown by XMCD experiments, a magnetic transition is observed at 2 Mn monolayers. The analysis of RHEED and SEXAFS experimental results clearly demonstrates that a structural transition comes with this magnetic transition.

Anisotropie short-range structure in Co-Pd alloy and Pd/Co multilayer films is determined using polarized Co K-edge extended x-ray absorption fine structure. A local modulation of Co fraction exists along the growth direction in the alloy films. Pd underlayer and Pd spacers alternated with the alloy layer influence an effective strain anisotropy. Pd/Co multilayers have an alloy-like region near nominal interfaces by diffuse interface. Pd spacers in the multilayer play a role in coherency strain rather than on broken symmetry of Co atoms. Local structural anisotropy of both strain and chemical environment contribute to the perpendicular magnetic anisotropy observed in these films.

Results of theoretical investigations on the magneto-optical Kerr-effect in layered systems are presented that are based on a fully relativistic description of the underlying electronic structure. To investigate the importance of the various sources of the Kerr effect model calculations have been performed. Applications to multilayer systems have been done for systems with non-magnetic spacers having a relatively high (Co/Pd, Co/Pt) as well as a small induced magnetic moment (Co/Cu) and comparison with experiment is made. To investigate surface layer systems the use of auxiliary model multilayer systems is explored.

Recent results on the dependence of the magnetic circular dichroism on the angle and temperature for thick (100 ML) films of Gd(0001) are presented. Strong dichroic effects were observed in 4d core-level photoemission for the magnetized films, which showed excellent agreement with an atomic many-particle description recently published [1]. The angular dependence of the magnetic dichroism has been discussed taking into account photoelectron diffraction effects. In addition, an indication of a higher surface Curie temperature has been observed in the temperature- dependent measurements.

MCD spectra at the M2,3 edge of thin Fe films exhibit thickness-dependent variations in line shape as well as in the absolute MCD-effect. Our data indicate that more information is contained in the MCD spectra than simply the evolution of a magnetic moment and ferromagnetic order. We developed a model to predict line shape modulations as a function of film thickness and angle of light incidence. Using the Fresnel-Maxwell formalism we calculate interference effects between left and right circularly polarized light reflected from the vacuum-film-substrate interfaces which are verified by our MCD measurements. Since the observed interference effects are a function of the excitation wavelength, our results can be directly scaled to show the significance of these effects in the more commonly used L2,3 region of 3d ferromagnets. Our data point out that one might be ill advised to rely onL2,3 MCD experiments to try to extract the formation of magnetic moments in films of several 10s of Å in thickness.

In-situ scanning tunneling microscopy (STM). magneto-optical Kerr effect (MOKE) and Kerr microscopy are used to investigate the relations between structure, morphology, and magnetism in low-temperature (LT) grown Fe/Cu(100) films. At the spin reorientation thickness of ≈ 3.8 monolayers (ML) Fe/Cu(100) the coexistence of in-plane and out-of-plane magnetized domains is observed. For Fe thicknesses between 3.8 and 6 ML Fe/Cu(100). an irreversible spin reorientation from in-plane to out-of-plane can be induced by annealing up to 420 K. Annealing of LT-grown Fe/Cu(100) films is proposed to provide smooth surfaces for Cu/Fe/Cu(100) sandwich preparations.