Thick films (0.6 and 2.0 μm) of the colossal magnetoresistance (CMR) material, La0.7Ca0.3MnO3 (LCMO), have been grown by pulsed laser deposition (PLD). The films were grown from single-phase LCMO targets in 100 mTorr 02 pressures and the material deposited on (100) LaAlO3 substrates at deposition temperatures of 800°C. The deposited films were characterized by X-ray diffraction (XRD), magnetic field-dependent resistivity, and Rutherford backscattering spectroscopy (RBS). The LCMO films were shown by XRD to adopt an orthorhombic structure. Brief post-deposition annealing led to ~50,000% and ~12,000% MR effect in the 0.6 μm and 2.0 μm films, respectively.

Epitaxial Nd0.7Sr0.3MnO3-δ and La0.67Ba0.33MnO3-δ thin films with large magnetoresistance ratios have been prepared by pulsed laser deposition. Huge negative magnetoresistance ratios of -ΔR/RH > 1×106 % were obtained at 60 K and a magnetic field of 8 T in a Nd0.7Sr0.3MnO3-δ film. The influence of sample preparation conditions on the resistivity behavior of these films has been studied. Results suggest that oxygen stoichiometry and diffusion are important factors in causing the behavior observed in doped manganese oxide films.

We have calculated the electronic structure, total energy, magnetic moments and electrical resistivities of La.67Ca.33MnO3 using mean field band theory. The magnetic and structural properties seem to be in good agreement with experiment. The calculations predict that La.67Ca.33MnO3 is metallic for the majority spins and semiconducting for the minority spins.

A practical atom specific surface magnetometry can be based on the measure of magnetic dichroism in the angular distribution of core photoelectrons using linearly polarized synchrotron radiation. The magnetic dichroism effect on the photoemission intensity of 3p core levels of the ferromagnetic transition elements is as large as 46% in the case of Fe(100). The most efficient scheme for measuring the magnetic dichroism in photoemission requires two mirror experiments in chiral geometry, i.e. only two times more experiments than standard core level photoemission for surface chemical analysis. We describe the dichroism magnetometry and show examples for Fe, Co, Ni and Cr surfaces and interfaces, including the measurement of the temperature dependence of the Fe(100) surface magnetization and of the effect of S-segregation on the surface magnetic moment of iron.

In the recent past, Carra, et al. derived a sum rule for electric dipole transitions in a single ion model that could be used to extract an elementally-specific spin-magnetic-moment (μSPIN) from magnetic x-ray circular dichroism (MXCD) spectra. Earlier, we proposed the utilization of a branching ratio analysis for the determination of μSPIN, based upon a simplified oneelectron, atomic picture which assumed complete orbital quenching. Here, it will be shown that these two approaches are essentially related in the case of 3d ferromagnetic materials. Both methods are based upon a comparison of the integrated intensity in the L3(J=3/2) white line peak versus the sum of the intensities in the L3(J=3/2) and L2(J=l/2) peaks, after background removal. An error estimate will also be presented. A more complete description of our work is under preparation.

Continuously tunable multilayer linear polarizers extend magneto-optical rotation techniques into the extreme ultraviolet and soft x-ray regions. Resonant magneto-optical rotation is large at the Fe L2,3 edges. Magneto-optical Kerr rotation can be either bulk or surface sensitive depending on incidence angle. A SMOKE hysteresis loop measured from the Fe in an Fe/Cr multilayer reveals high sensitivity and a complex magnetic response of Fe.

197Au Mössbauer measurements have been performed for Au/Fe, Au/Co and Au/Ni magnetic multilayers. 197Au Mössbauer spectra observed from multilayers consist of at least 4 components having different magnitude of hyperfine fields and isomer shift values those depend on the local environments of the Au probe-atoms in multilayers. Rather large electron spin polarization at Au atoms has been observed in the interface with adjacent ferromagnetic layers, but nearly no magnetic hyperfine field has been observed to the interior of Au layer. It implies that the largest hyperfine field observed is not due to the conduction-electron polarization but induced by the hybridization in the interface with ferromagnetic layer.

We show theoretically that the change in the magnetization structure of magnetic metallic multilayers under the application of a magnetic field shall be generally associated with a significant change of the refractive index. This constitutes a new magnetooptical effect: the magnetorefractive effect.

Optical transmission measurements under an applied magnetic field through [Ni80Fe20/Cu/Co/Cu] multilayers, in the light wavelength region between 2 μm and 20 μm, clearly demonstrate the existence of the predicted effect and are found in reasonnable agreement with the theoretical calculations.

The signal measured during a Magneto-Optic Kerr Effect (MOKE) experiment is usually assumed to be linear in the magnetization (or the magnitude of the magneto-optic coupling vector Q that is proportional to the magnetization) so that a plot of the magnetization versus applied field can be obtained. We have observed an appreciable contribution from the Q2 term in the magneto-optic response of epitaxial Fe(110)/Mo(110) bilayers. The Q2 term in the magneto-optic response is much larger than that predicted by existing theory. We re-derive and modify the existing theory to fit the Q2 term.

We present an electromagnetic enhancement mechanism for the magneto-optical response of noble metal / ferromagnetic metal multilayer thin films. When such a structure is illuminated in total reflection condition, the resonant coupling of light with the noble metal surface plasmons gives rise to an amplification of the magneto-optically induced component of the light electric field. The experimental results obtained on a 30nm-thick Au / Co / Au model system show that this resonant feature observed in the Kerr rotation and ellipticity corresponds to a strong enhancement of the magneto-optical figure of merit and signal-to-noise ratio.

With appropriate processing conditions, nanoscale ferromagnetic particles precipitate from nonmagnetic matrix phase in the Co-Cr and Cr-Fe systems. In these heterogeneous alloys, unique magnetic properties are observed. In order to correlate such magnetic properties with the microstructures, we have employed an atom probe field ion microscope (APFIM) and a three dimensional atom probe (3DAP). In the Co-22Cr thin film sputter-deposited at elevated temperatures (~500 K), both APFIM and 3DAP data convincingly showed that the film was composed of lamellae-like ferromagnetic and paramagnetic phases of approximately 8 nm in thickness. On the other hand, it was shown that the films sputter-deposited at ambient temperature was composed of s-Co single phase without significant compositional heterogeneity. Based on these observations, we conclude that phase separation progresses during the growth of the film on a heated substrate. In the Cr-Fe alloy, large negative MR was observed in the as-quenched alloy at liquid helium temperature. However, the MR behavior changes as the phase decomposition progresses by annealing. The change in the MR behavior observed in this alloy with various heat treatment conditions will be discussed based on the microstructural characterization results by APFIM and 3DAP.

An unconventional technique combining Mossbauer spectroscopy with the effects induced by magnetic radio-frequency fields (if collapse and if sidebands) is employed to study the microstructure and magnetic properties of nanocrystalline clusters of bcc Fe formed by annealing amorphous Fe93-x-yZr7B,xCuy (x=6, 8, 12, y=0, 2) alloys at 500-600°C. The rf-Mössbauer experiments allow us to distinguish magnetically soft nanoclusters from magnetically harder microcrystalline phases. The dependence of the bcc Fe phase formation on the alloy composition is discussed. The Mössbauer results are supplemented by DSC measurements.

The magnetic properties of alkali-doped zeolites have been investigated using magnetic resonance spectroscopy. Although paramagnetic centres have been detected, the predominant species, in many cases, is spin-paired.

This investigation has looked at the preparation of nanoscale cobalt particles by a simple solid state reaction involving cobalt (II) nitrate and zeolite Na-X under vacuum conditions followed by reduction in an hydrogen atmosphere. Samples were characterised by powder x-ray diffraction and scanning/transmission electron microscopy (TEM). Magnetic measurements were performed on the samples below 300 K using a SQUID magnetometer.

The electronic structure and magnetic properties of rhodium clusters with sizes of 1 - 43 atoms embedded in the nickel host are studied by the first-principles spin-polarized calculations within the local density functional formalism. Single Rh atom in Ni matrix is found to have magnetic moment of 0.45μB. Rh13 and Rhl 9 clusters in Ni matrix have lower magnetic moments compared with the free ones. The most interesting finding is tha.t Rh43 cluster, which is bulk-like nonmagnetic in vacuum, becomes ferromagnetic when embedded in the nickel host.

Studies of the evolution of electrical resistance in an external applied magnetic field, B, as well as with temperature, T, on Cu86Co14 and Cu92Co8 as quenched and annealed melt-spun ribbons, reveal that magnetoresistance, MR, ΔR(B,T)=R(B)-R(0) scales with B/T. Furthermore, it found that annealing up to 600 °C scales the magnetic moment of the Co-rich superparamagnetic nanoparticles such that, the data for the field dependence of the MR obtained at various temperatures collapses onto the same unique and universal curve f(mB/T) with the Langevin variable mB/T governing the overall behaviour.