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Nanostructured magnetic materials are intensively studied due to their unusual properties and promise for possible applications. The key issues in these materials relate to the connection between their physical properties (transport, magnetism, mechanical, etc.) and their chemical-physical structure. In principle, a detailed knowledge of the chemical and physical structure allows calculation of their physical properties. Theoretical and computational methods are rapidly evolving so that magnetic properties of nanostructured materials might soon be predicted. Success in this endeavor requires detailed quantitative understanding of the magnetic structure and properties.

We studied the effects of Mn concentration ([C.sub.Mn]) in PtMn antiferromagnets (AFs) and the deposition temperature ([T.sub.s]) of PtMn in bottom PtMn spin valves. The exchange coupling field ([H.sub.ua]) and the critical thickness of PtMn were found to depend strongly on [C.sub.Mn]. Spin valves made with the optimum [C.sub.Mn] (51%) show an [H.sub.ua] value of around 410 Oe even with 125-[Angstrom]-thick PtMn, compared to the saturation value of about 500 Oe for the spin valves with much thicker PtMn. For the [T.sub.s] dependence study, the NiFeCr-NiFe underlayer, PtMn AF layer, and part of the CoFe pinned layer were deposited at [T.sub.s], up to 300[degrees]C, and the rest of the layers were deposited after cooling the spin valve down to ambient temperature. The spin valves deposited at [T.sub.s] >250[degrees]C and with > 150-[Angstrom]-thick PtMn show [H.sub.ua] of around 250 Oe, as deposited (without postannealing). The [H.sub.ua] values increase upon postannealing for the spin valves deposited at all the [T.sub.s] studied (25[degrees]C-300[degrees]C). However, the ferromagnetic coupling field ([H.sub.f]) also increases with repetitive postannealing, the rate of [H.sub.f] increase being lower for the spin valves deposited at higher [T.sub.s]. The sheet resistance of PtMn spin valves was found to increase both after postannealing and with increasing [T.sub.s], consistent with the higher resistivity observed for thin PtMn films deposited at higher [T.sub.s]. These results are attributed to the smaller grain size and the higher degree of chemical ordering for PtMn in the postannealed spin valves deposited initially at higher [T.sub.s], as deduced from X-ray diffraction. Index Terms--Deposition temperature, Mn concentration, PtMn antiferromagnet, PtMn resistivity anomaly, PtMn spin valves, PtMn thickness dependence.

An analytical model is developed to analyze the effects of viscous flow on residual stresses in film-substrate systems. Compared to viscous flow in the film, viscous flow in the substrate results in slower stress relaxation in the system.

Porous silicon (PS) made from doped material is modeled as a uniaxial effective medium consisting of hollow cylindrical silicon shells and free cylindrical pores. Diffuse reflectance of a porous layer at its interface with air agrees with measurements of light scattering from p(super +) porous silicon at a wavelength gamma = 457 nm.

Diffuse x-ray scattering around Bragg peak (004) is investigated for p(super -)- and p(super +)-type silicon samples. The porous silicon (PS) crystallites are stressed along the q(sub z) direction and relaxed along the lateral q(sub x) direction.

Room temperature Brillouin light scattering measurements designed to probe the elastic properties of chemically ordered Co3Pt alloy films was investigated. Between 450 and 950k, the film stabilizes with structures that are packed to a disordered fee phase.

The correlation between the magnetic viscosity in CoPtCr thin film media and the concentration of local fcc-like regions was described. Results showed that the concentration of the defects was varied by growth on different underlayers and was measured with grazing incidence x-ray scattering using synchrotron radiation. It was shown that a substantial percentage of local fcc regions in a cobalt alloy film leads to a significant magnetic viscosity effects at modest magnetic fields.

A study is conducted on the film growth of fully chemically ordered FePt (001) epitaxial thin films. Results show that these films have high degree of expitaxy and chemical ordering. Highly interconnected magnetic stripe domains with magnetization perpendicular to the film were found in films thicker than 50nm, which lead to characteristic low remanence magnetization curves. Two mechanisms that lead to irregular domain patterns and high remanence and coercivity in the polar hysteresis loops are also determined.

Microstructural and magnetic characterization of FePt (110) films deposited onto platinum seed layers on MgO (100) substrates, at 300 and 500 degrees Celsius, were carried out in experiments. An FePT(110)-oriented film grown at a substrate temperature of 300 degrees Celsius was found to be in a state of inhomogeneous chemical order. The inhomogeneous chemical ordering and the small size of ordered and partially ordered regions is expected in view of likely microscopic variations of the growth surface.

Magnetoresistance (MR) of (111)-oriented multilayers consisting of ferromagnetic films of Permalloy-silver with Ag spacer films is influenced by the annealing and growth temperature. Negative MR is exhibited by the multilayers in the As-grown state, which increases significantly with the increase in growth temperature. The annealing improves the structural order, decreases the laminar order and partially segregates the Ag from the ferromagnetic films into nearby Ag films. MR does not produce discontinuities in the magnetic layers.

Research into enhancement of giant magnetoresistance properties of single (bottom) and dual IrMn-based spin valves through exposure of part of the CoFe pinned layer to O2 is presented. It was found that the interface between Cu spacer and free layer seems to be most susceptible to the O2-induced smoothing effect.

Ion beam patterning of magnetic thin films through suitable stencil masks is suggested as a prospective path towards patterned, ultrahigh-density magnetic recording media. Co/Pt multilayers, in particular, are ideally suited for the application, since bombardment with a suitable dose of energetic ions may induce interface mixing, thereby triggering a spin-reorientation transition from easy axis out-of-plane to easy axis in-plane.

The magneto-optical spectra of chemically ordered FePt (001) and FePd (001) compounds are studied. The imaginary part of the off diagonal element, [[Sigma].sub.2xy] of the conductivity tensor has two peaks located in the energy ranges 1.2 - 2 eV (Fe-like transitions) and 4 - 4.5 eV (Pt or Pd like transitions). The strength of these peaks is larger in FePt than in FePd and roughly scales with the spin orbit coupling of Pt and Pd d-bands in the ultraviolet spectral range. Large differences in the Fe dominated low energy side of the spectra suggest a much higher degree of electronic hybridization in FePt than in FePd.

Chemically ordered, self-assembled FePt nanoparticle arrays with high magnetic anisotropy are considered as a candidate medium for data storage beyond 1 Tbit/in². We report comprehensive structural and magnetic studies on thin (three-layer) assemblies of polyethylenimine (PEI) and 4 nm Fe58Pt42 nanoparticles using x-ray diffraction, small angle neutron scattering, and magnetometry. We show that prior to annealing FePt nanoparticles in the PEI-FePt assembly consist of a metallic magnetic core surrounded by a weakly magnetic or nonmagnetic shell. High temperature annealing creates the desired L 10 chemical ordering and results in high coercivity FePt nanoparticles. However, we find that the high temperatures necessary to establish full chemical ordering leads to particle sintering and agglomeration. Understanding the magnetic and physical properties of these assemblies allows future research directions to be clarified for nanoparticle arrays as data storage media. [ABSTRACT FROM AUTHOR]

High resolution and grazing incidence x-ray scattering experiments are performed to examine the magnetostructural coupling in (110) europium film. The grazing incidence is used for showing that the structural characteristics are nonhomogeneous with the film depth, the dominant structural domain being different in the top and bottom parts of the film.

Two series of epitaxial CoPt and FePt films, with nominal thicknesses of 42 or 50 nm, were prepared by sputtering onto single-crystal MgO(001) substrates in order to investigate the chemical ordering and the resultant magnetic properties as a function of alloy composition. Conclusion reveals that nonstoichiometric L1(sub 0) CoPt and FePt, with a slight excess of Co or Fe, are preferable for applications requiring the highest anisotropies.

The electrical resistance and the microstructure of copper thin films deposited in an oxygen-containing atmosphere by ion-beam and dc-magnetron sputtering is reported. The dc-magnetron-produced films have higher resistivity, have smaller Cu grains, and contain a higher concentration of cuprous oxide particles.

The Silicide formation and particle size growth in high-temperature-annealed, self-assembled FePt nanoparticles is discussed. Silicide formation as a result of a chemical reaction with the native oxide or Si substrate leads to a substantial drop in magnetization for T(sub anneal)>650 degree C.

The onset of chemical ordering due to annealing of FePt nanoparticle assemblies is discussed. It is found that much of the Fe in the as-synthesized particles is partially oxidized, and the degree of oxidation is chemically reduced with increasing annealing temperature.

A phase instability in oxygen-plasma-assisted molecular beam epitaxy of Fe(sub 3)O(sub 4)(111) films on sapphire(0001) substrates is reported. The magnetic properties of Fe(sub 3)O(sub 4) films depend strongly on growth orientation and on the phase separation. Fe(sub 3)O(sub 4)(111) films, whether single or mixed phase, are much more difficult to magnetize compared with Fe(sub 3)O(sub 4)(001) films grown under identical conditions.

Discusses the magnetic domain structure and magnetization curves of chemically ordered epitaxial iron platinum (FePt) films with perpendicular magnetic anisotropy. X-ray diffraction; Influence of seed layers; Film thickness dependence.

An investigation on structural and temperature dependent magnetic properties of chemically ordered epitaxial Fe(sub 55-x)Ni(sub x)Pt(sub 45) thin films. The ability to control thermomagnetic properties over a wide range makes Fe(sub 55-x)Ni(sub x)Pt(sub 45) and similar FePt-based pseudo-binary alloys attractive base materials for media applications in thermally assisted magnetic recording.

The use of a thin [([Ni.sub.0.81][Fe.sub.0.19]).sub.1-x][Cr.sub.x] seed layer for obtaining high anisotropic magnetoresistance in Permalloy ([Ni.sub.0.81][Fe.sub.0.19]) films is reported. The process yields a high [Delta] R/R of, for example, 3.2% for 120-[Angstrom]-thick NiFe, without high-temperature deposition or annealing. X-ray diffraction shows that the NiFeCr seed layer causes the formation of large (111) textured grains in the Permalloy film, and that the interface between these two layers is quite smooth. These both increase the [Delta] R and reduce the resistance R in the film, which lead to the high [Delta] R/R. Also discussed is the enhanced [Delta] R/R and thermal stability trilayer magnetoresistive sensors using this NiFeCr instead of Ta as a spacer. Index Terms--Anisotropic magnetoresistance, Permalloy film, seed layer.