The nonlinear Magneto-optical Kerr-effect (NMOKE) has been proven to be an ultrafast spectroscopie probe of the magnetic and electronic properties of ferromagnetic surfaces. Extending our previous theory we calculate the linear and nonlinear Magneto-optical Kerr-spectra of Fe. The results for the nonlinear Kerr spectra are compared with recent experiments on a Fe (110) surface. We derive and discuss general features of the nonlinear Kerr-effect, especially the details of its dependence on exchange interaction and Fermi-level crossings in the Stoner picture and beyond, frequency, and spin-orbit interaction. Furthermore we demonstrate how various electronic material properties, such as d-band width, s-d hybridization or band narrowing due to electronic correlations or caused by geometry (reduced coordination number in thin films), can be extracted from the spectra. As an example, we compare the linear and nonlinear Kerr-spectra of Fe to those of Ni. The extension of our theory to the Kerr spectra of thin magnetic films films as well as of hidden magnetic interfaces occurring in sandwiches and multilayers is discussed.

With spin polarized electron spectroscopies, we have investigated ordered Gd (0001) films deposited on W (110). The photoemission features of the gadolinium 5d surface state, the 4f levels, and the background exhibit considerable spin polarization along the same direction in the plane of the film, indicative of ferromagnetic coupling between the surface and the bulk. The 4f spin polarized photoemission data provides strong evidence that the surface 4f polarization differs from the bulk 4f polarization for Gd (000l). Our temperature dependent measurements with spin polarized secondary electron spectroscopy conclusively establishes that the surface of clean Gd (0001) possesses a perpendicular polarization component which persists to an enhanced surface Curie temperature. SMall amounts of contamination at the surface result in the disappearance of the perpendicular component and, therefore, a more perfect ferromagnetic coupling between the surface and the bulk.

We have characterized magnetization loops of epitaxially grown Gd (0001) films on W (110) in the temperature range 145≤T≤300K. This was accomplished by measuring magneto-optical Kerr loops in UHV, in the transverse geometry, using a 2×10-4 deg sensitivity differential detector and He-Ne laser light.

Films grown in the Stranski-Krastanov (SK) Mode (growth temperature 400°C) and films grown in a Frank-van-der-Merwe (FM) like Mode (growth temperature 20°C) behave significantly differently. While the room temperature grown films (FM) show square hysteresis behavior only after an annealing cycle to at least 300°C, the higher growth temperature (SK) leads to highly remanent films in the as grown state.

The hysteresis behavior of these films is most important in conjunction with recently reported spin-polarized photoemission results, which showed that the growth temperature and therefore the film morphology has a strong influence on the surface magnetic reconstruction of Gd (0001) [1].

We have calculated numerical simulations and analytical solutions of the influence of a pin hole on the magnetization curves of multilayer systems. The Magnetization curves we obtained can be described by a biquadratic coupling model and are close to the experimental curves.

In this paper, the synthesis of a new structure of iron in (100) Felr superlattices grown by Molecular Beam Epitaxy is reported. Two-dimensional growth up to 4 planes at 400K occurs, as shown by RHEED oscillations. Electron diffraction also gives evidence that the Fe lattice is pseudomorphic to the Ir one during the 2D-growth, and relaxes to the bcc lattice for thicker deposits. An X-Ray analysis shows that the Fe structure is a body centered tetragonal one with a c/a ratio close to 1.25. This phase is observed to be non-Magnetic at room temperature, as a weak ferromagnetic behaviour is observed at low temperatures, except at small Ir thicknesses. This is the evidence of the existence of a low spin phase which seems to undergo a second order phase transition with the atomic volume of iron.

We present a calculation of spin waves in coupled multilayered structures which is based on exact evaluation of both exchange and dipolar fields. The ground state spin configuration in antiferromagnetically coupled multilayers can differ significantly from the uniformly canted ground state usually assumed. This non-uniform ground state is found to radically alter the character of the spin wave modes and sometimes lead to a strong localization of the wave to the outermost magnetic films of the Multilayer.

The lattice reconstructed bec Ni (001) in Fe/Ni (001) ultrathin layers allows one to engineer films in which the in-plane 4-fold anisotropies and coercive fields can be varied and adjusted according to specific requirements. Magnetization reversals have been studied in layered structures of Fe/Ag/Fe/Ni (001). For Ag (001) interlayers thicker than 13 ML Magnetization reversal can proceed in two steps. In these samples the minor loops switch the magnetization of the Fe (001) layer from the parallel to the antiparallel configurations with respect to the magnetic moment of the Fe/Ni film. Such Minor loops exhibit a rectangular behavior with switching fields of 15–25 Oe. The lattice transformed Fe/Ni layers could be useful in spin-valve structures.

We demonstrate that the photon energy dependence of the polar Kerr effect can be used as a sensitive probe of chemical ordering effects in binary intermetallic alloys. We demonstrate this effect in the Co50Pt50 alloy, which is known to have a Ll0 phase (critical temperature ∼825°C). Kerr spectra of the ordered and disordered phases of the Co50Pt50 alloy composition differ drastically from each other and the ordered phase shows an unprecedented, new peak at 2.2eV photon energy. The intensity of this new peak correlates with the degree of chemical ordering and the magnetic anisotropy in these films.

The Magneto-optical Kerr effect of CoPt3 ordered compounds and alloys is investigated experimentally and analyzed theoretically using first principles band structure calculations.

The calculations confirm the experimental results and allow for the first time a detailed, bandstructure based interpretation of the electronic transitions leading to the well known strong uv peak at around 4eV. This feature can be unambiguously attributed to Magneto-optical transitions within the Pt p and d bands.

We have successfully grown thermodynamically stable ferromagnetic MnxGa1-x (x=0.55∼0.60) thin films with thicknesses ranging from 3 nm to 60 nm on GaAs substrates by molecular beam epitaxy. The c-axis of the tetragonal structure of the MnGa film is shown to be aligned perpendicular to the substrate. Both Magnetization Measurements and extraordinary Hall effect measurements indicate perpendicular magnetization of the MnGa films, exhibiting squarelike hysteresis characteristics. Furthermore, we have investigated the effect of Ni additions as a substitution for mn in (Mn60-yNiy) Ga40 alloy thin films with y=0 – 30 at% Ni. With increasing Ni, the perpendicular component of the magnetization becomes smaller up to y=18 where the magnetization is in-plane. At y=30, the magnetization is again perpendicular.

The effect of magnetic coupling in Multi-layer system is discussed by an analytic approach and computer simulation. The dependence of the enhancement of external field on the magnetic properties of the relevant materials is studied. Comparison between the theoretical estimate, simulation result and experimental observations are presented.

Cobalt-platinum alloys and multilayers are now well known for their potentialities in Magneto-optical recording Media. The growth of ultrathin layers and sandwiches is thought to be useful to find the relationship between the structural and magnetic properties at an atomic level. Low Energy Electron Diffraction (LEED) and Auger spectroscopy (AES) are used here to study the crystallography and the growth modes of Pt on Co (0001) surfaces. Co/Pt/Co sandwiches are also built and investigated by the same Methods. At room temperature we show the evidence of a good epitaxy of platinum on the Co (0001) surface leading to the possibility of obtaining ordered Co/Pt/Co sandwiches. Annealings at moderate temperatures lead to an epitaxial alloy formation. Auger results show that alloying indeed induces a magnetic moment on platinum atoms. This could explain the magnetic properties already observed in CO/Pt (111) Multilayers.

Magnetic properties and roughness of sputter-deposited Pt/CO films strongly depend on preparation conditions such as rf input power, underlayers and their etching. Large coercivity was obtained by using suitable underlayers such as ZnO and adjusting input power higher for Co and lower for Pt. The coercivity in Pt/CO films seems to depend on the roughness of the surface and/or the layer interface as well as the perpendicular anisotropy.

We have used in situ polar Kerr effect measurements to study the magnetic coercivity and anisotropy of MBE-grown Pd (111) /Co/X and Au (111) /Co/X trilayers, where χ is the nonmagnetic noble or transition metal overlayer Ag, Cu or Pd. Polar hysteresis curves were Measured in situ for systematically varied Co and overlayer thicknesses 2 Å ≤ tco ≤ 20 Å and 0 Å ≤ tx ≤ 50 Å. We find the coercivity and total anisotropy display a strongly peaked perpendicular contribution at ∼1 atomic layer (2 Å) non-Magnetic Metal coverage. For Cu, where the effect is strongest, the total anisotropy energy rapidly decreases by a factor of 3 from its peak value after a total coverage of ∼2 atomic layers (4 A) of Cu.

In the exciting field of low dimensional magnetic systems including surfaces, interfaces and thin-films, local spin density (LSD) functional ab initio electronic structure calculations have played a key role by not only providing a clearer understanding of the experimental observations but also predicting new systems with desired properties. Our extensive calculated results demonstrate that: (i) Magnetic clean surfaces or interfaces with inert substrates undergo strong magnetic moment enhancements; (ii) the strong interaction with nonmagnetic transition metals diminishes (completely in some cases) the ferromagnetism and usually stabilizes the antiferromag-netic configuration. By including spin-orbit coupling as a perturbation, (i) reliable results for the Magneto-crystalline anisotropy of ultra-thin films can be obtained using the state-tracking procedure, although the anisotropy energy is a few tenths of a MeV; (ii) spectra of the Magneto-optical Kerr effects and magnetic circular dichroism in the soft x-ray region can be determined.

A unified explanation is given of the long-standing question of the origin of the low-field magnetoresistance, MR, behavior in pure ferromagnetics and the large magnetoresistance effects seen in magnetic layered and granular structures. It is shown that the main contributions to these effects are due to the scattering that occurs at the magnetic boundaries between non-aligned magnetic regions. This scattering occurs because the predominant conduction electrons in 3d ferromagnetics are the highly polarized itinerant d electrons. As a result of this polarization the Majority-band d electrons are strongly reflected at an antiparallel magnetic boundary due to a lack of available states for occupancy. The traversing electrons are further scattered as they cross the boundary due to a discontinuity in the potential caused by the interchange of their kinetic and exchange energies at the boundary. Expressions for the magnetoresistance due to these scattering mechanisms are derived and shown to describe very well the wide variety of magnetoresistance values and other features found in the literature for both pure Fe and nano-structures of Fe or Co with non-Magnetic Materials. The MR Magnitude is seen to vary inversely with the domain size. Thus the domain size and sample purity are seen to be the main factors that determine the magnitude of the MR effect in pure ferromagnets. The large MR values seen in layered and granular magnetic structures arise from the small effective domain size attainable in these structures. This is achieved by introducing a non-Magnetic Material into these structures which allows the effective domain size to be decreased from the micron range of the pure ferromagnetic elements into the nanometer range.

Recent results from spin polarized electron spectroscopie studies of surfaces and ultrathin films are presented. The Magnetic coupling of 3d transition Metals (Cr,Mn) to the Fe (100) surface is studied by spin polarized electron energy loss spectroscopy. The first atomic layer of Cr and mn aligns antiparallel to the Fe. For larger thicknesses we find evidence for layer-by-layer antiferromagnetic order. In the range of 1–6 atomic layers the behavior is more complex with the surface of the Cr films showing preferential ferromagnetic alignment while the mn surface aligns antiparallel to the Fe substrate.

Secondary electrons from Gd (0001) surfaces are shown to be highly spin polarized. However, no enhancement mechanism at low kinetic energy as in the 3d transition metals is observed indicating the absence of strongly spin dependent inelastic scattering in Gd. Temperature dependent spin polarized 4f photoemis-sion results show almost complete polarization demonstrating ferromagnetic surface coupling. However, a perpendicular surface magnetization component is found indicating surface spin canting. A large enhancement of the surface Curie temperature is also present.

Spin-Polarized Metastable Atom Deexcitation (SPMDS) and Electron Capture (ECS) Spectroscopies probe the exponential tails of electronic wavefunctions extending from the surface into the vacuum, and are consequently extremely sensitive to the surface-vacuum interface. The use of SPMDS to probe the near-surface vacuum magnetization of Ni (l 10) and Fe (l 10) and the dramatic changes that result upon exposure to ambient gases is discussed, as is the use of ECS and Spin-Polarized Electron EMission Spectroscopy (SPEES) to determine the ferromagnetic and critical behavior of surfaces and ultra-thin epitaxial systems.

The first spin-resolved x-ray photoelectron spectroscopy (SRXPS) study of the n = 2 core levels of ferromagnetic Fe are reported. The 2p3/2, 2p1/2 and 2s core levels all display interesting spin-dependent structures and splittings. The spectral complexity predicted by a purely atomic picture is not observed in the data. The results indicate that theories incorporating the delocalization of the 3d valence band are more applicable to the description of core-level photoemission in iron.

The origin of the Rh polarization at the interface with Fe is discussed within a self-consistent mean-field parameterized tight-binding model. Since experimentally it is not yet known how Rh grows on Fe (001), in this paper we consider both fee and bec growth. When Rh grows in the fee structure, it expands its lattice parameter and a polarization is present up to 3 layers, whereas in the bec case only the Rh atoms at the interface are polarized. The results obtained are compared to recent spin- and angle-resolved photoelectron spectroscopy experiments. Good agreement with experiment is obtained in the case of a fee Rh configuration.