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The complete spin polarization of half metallic ferromagnets is destroyed by finite-temperature spin disorders. Polarization declines at finite temperatures due to magnon and phonon effects and hence half-metallic ferromagnetism is limited to zero temperature.

A nucleation-based analytical methodology helps enhance the magnetic strength of aligned two-phase magnets by exchange hardening in nanoscale combinations of a soft-phase and an oriented hard-phase. Breakdown of this high energy magnet occurs in the limit of isotropic magnets having enhanced remanence. The high cost of production of such giant-energy magnets limits their range of application.

The study of the reaction between nitrogen gas and an intermetallic compound with particular reference to Sm2Fe17, treating the Sm2Fe17N(sub y) system as a gas solid solution, shows that there is a large uniaxial strain near the surface of nonuniformly nitrided particles and even in the absence of nitrogen there is core expansion. The reaction of nitrogen atoms with the metal lattice in terms of the net reaction energy U(sub 0) is described by a simple lattice gas models. The equilibrium nitrogen concentration as a function of nitrogenation temperature and gas pressure is calculated.

The structural and magnetic properties of substituted [L1.sub.0] compounds are studied. It is shown that ordering has a strong impact on the magnetism of the alloys, particularly on the anisotropy.

Magnon-plasmon interactions are modeled by considering the spin-dependent dielectric response of atom placed in crystalline environment. Magnetic excitations of intra-atomic origin are analyzed which are found to be related to ordinary magnons but involve longitudinal magnetic degrees of freedom and involve much higher energies.

The temperature dependence of the magnetic anisotropy of ferromagnetic materials is analyzed. The findings conclude explain that magnetocrystalline anisotropy is, essentially, a single-ion property by embedding the atom in a metallic or nonmetallic crystalline environment.

Electron microscopy, x-ray diffraction and superconducting quantum interference device magnetometry are used for examining the FePt and Fe3O4 nanotubes produced by hydrogen reduction in nanochannels of porous alumina templates. Fe3O4 tubes are formed by a thermally decomposed Fe nitrate solution at 250 degrees C that is reduced in hydrogen for 2.5 h at the same temperature.

The magnetic properties and switching behavior of anisotropic magnetic nanodots are examined. A strong interdot interaction is observed in dot separations of less than 50 nm resulting in a probable controlled switching of neighboring dots.

Linear muffin-tin orbital calculations were used to examine the electronic band structure of ordered equiatomic compounds of 3d transition elements (Mn, Fe, Co, Ni) with nonmagnetic 4d and 5d elements (Rh, Pd, Pt, Ir). Mn spins in a given plane prefer to align antiferromagnetically as indicated by the pronounced negative exchange interactions between four Mn-Mn first nearest pairs, J(sub 11) observed in all Mn compounds.

Research into cooperative and noncooperative magnetization processes in magnetic nanostructures is presented. It is found that the Preisach model overestimates the coercivity. In general, cooperative effects are strongest for narrow switching-field distribution.

Research into the magnetism of antimony overlayers on a ferromagnetic substrate is presented. This approach produces a layer-specific analysis of the spin polarization. The relatively long range of the Sb spin polarization is attributable to the semimetallic nature of the Sb overlayer.

The net Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between well-separated spin distributions can be mapped onto a RKKY interaction between two point-like effective moments. In 4f metals and alloys, the RKKY interaction gives rise to a magnetoelectric two-ion anisotropy.

A study was conducted to analyze the effects of the shape of the energy landscape on the magnetic viscosity. The evolution of a quantum-mechanical system was characterized by the time-dependent Schrodinger equation. Experimental results indicated that the activation energy related to thermally activated hopping changes the magnetic viscosity by minimizing the attempt-frequency prefactor.

A study was conducted to analyze magnetic hardening in SmCo(sub x)-Co multilayers and heat treated nanocomposite films. The films were prepared by dc and rf sputtering. Magnetization loops were determined by an alternating gradient force magnetometer and a superconducting quantum interference device magnetometer. Experimental results indicated that a thick chromium underlayer is needed for magnetic hardening.

The diffusion of nitrogen in R(sub2)Fe(sub17) intermetallics by a method that reconciles the solid-solution and immobilization theories of nitrogen diffusion, has been studied. Two-sublattice diffusions may lead to sharp concentration profiles, although the phase structure of the nitride remains unchanged. There is a global relaxation time, that controls the smoothing of concentration gradients.

A lattice gas model was used to characterize interstitial modification of the rare-earth intermetallic compound R2Fe17Zx, R=Y,Sm and Z=N,C,B,Si and S. The results showed that solid-state reaction was the most promising method for introducing metalloids into intermetallic lattices. Solid-state reaction can be used at temperatures where hydrocarbon gases would destroy the lattice and features a large entropy of the gas.

The crystal field in the nitrogenated intermetallic compounds Sm2Fe17N3-delta and Sm(Fe11Ti)N1-delta was analyzed. The results showed that the intrinsic crystal field contribution per nitrogen atom was approximately at the same level in both intermetallics. This observation indicated that nitrogen provided a common mechanism of crystal field modification in both compounds. It was shown that charge penetration had negligible effects in the case of the local interstitial but was important in the polarization of non-4f orbitals.

The characteristics of Co/Pd multilayered thin films produced by pulsed laser deposition were investigated. The results showed that the material featured a (111) texture with diffraction patterns typical of a modulated period structure. At low field regimes, magnetoresistance was highly anisotropic and varied by -2% in the transverse configuration and +1% in the longitudinal configuration.

The role played by Zn in the formation of Zn-Fe phases in Sm2Fe17Nx permanent magnets was investigated using x-ray analysis and differential scanning calorimetry. The results showed that the coercivity of the magnet can be enhanced by heat treatment subsequent to the formation of the paramagnetic phase. An observed dip in the demagnetization curve indicated the possible presence of an additional paramagnetic phase.

Coercivity and nucleation fields for three-dimensional inhomogeneities in Sm2Fe17Ny permanent magnets were investigated. The results showed that linearized micromagnetic formulations can be used for calculating the nucleation fields. The lowest eigenvalue of the linearized problem yields the nucleation field. However, it was shown that nonlinear equations must be solved to achieve more realistic coercivity values.

Several model calculations are conducted to explain the different effects of nanostructuring on the magnetic entropy of the magnetic compounds and thin-film nanostructures. Most of the entropy of the compounds is shown to be localized near the grain boundaries.

Several model calculations are conducted to explain the impact of nanostructuring taking place on the various magnetostatic interactions taking place in the permanent magnets. The various mechanisms involved in the nanoscale magnetization processes are also discussed.

Several model and tight-binding calculations are conducted to determine the structural dependence of the magnetocrystalline anisotropy of the various itinerant permanent magnets. The strong oscillations of the anisotropy are shown to be completely tunable by alloying.

Several studies are conducted to explain the impact of interstitial nitrogen on the phase transition and the magnetocalroic effect observed in the Mn(As,Si) systems. The Curie temperature of the systems is shown to increase with nitrogen atoms and decrease with silicon addition.

Several studies are conducted to explain the permittivity and the permeability of the different Tb-doped and Fe core-shell nanoparticles. The addition of Tb atoms is shown to lead to significant changes in the electromagnetic materials constants and morphology of the nanoparticles.

Several model calculations are conducted to explain the mesoscopic Kondo effect occurring in the different metallic nanoparticles with a magnetic impurity. The magnetic susceptibility of these systems is also determined.

The studies related to optical, structural, and magnetic properties of two substantially different cobalt nanostructure thin films deposited at an oblique angle of incidence of 85 degree away from the substrate normal are reported. The results from comparison between an achiral columnar thin film grown without substrate rotation and a chiral nanocoil sculptured thin film by glancing angle deposition with substrate rotation are also presented.

Micromagnetic model calculations are used for examining the magnetism of magnetic surface alloys such as Fe-Pt on Pt(997). The studies have shown that for strong Dzyaloshinski-Moriya (DM) interaction, the zero-field spin structures have changed from uniform to a canted state with a wave vector, and a similar transition has occurred for weak DM interaction when the reverse external field has approached the nucleation field.

The nanostructure and magnetism of [L1.sub.0]-ordered FePt crystallites in matrices of Au and C are examined as a function of the Au and C contents. The magnetic force microscopy images have shown that the slope decrease is accompanied by a reduction in the magnetic correlation length, which is due to the reduced intragranular exchange coupling.

Chromium-doped hydrogenated diamond-like carbon (Cr-DLC) and chromium carbide hydrogenated DLC alloys are prepared by plasma-assisted vapor deposition and examined by x-ray absorption near edge structure spectroscopy and superconducting quantum interference device (SQUID) magnetometry. The heterojunctions have displayed negative magnetoresistance that saturates at than 500 Oe and is suitable for spin-electronics applications.

Model calculations are used for examining the effect of semihard magnetic phases and interphases on the performance of nanostructured two-phase permanent magnets. Very hard nanostructured magnets are created from soft phases with negative but large anisotropy constants.

The growth and magnetism of nanosize Fe clusters on Pt and other metal surfaces are examined. The results have provided ways to control the magnetism of small clusters with the substrate.

The magnetism of ultrasmall Co:CoO core-shell nanoclusters is examined. The proteretic behavior and its particle-size dependence have reflected a subtle interplay between various anisotropies and exchange interactions in the Co and CoO phases and at the Co-CoO interface.

Model calculations are used for examining the magnetization reversal in graded magnetic-recoding media and its effect on the areal density. The results have shown that the write-field reduction has negatively affected the areal density and a trade-off has remained between write field and bit size.

The preparation, structural phase transition and magnetic characterizations of heat-treated monodisperse FePt nanoparticles of 3nm size are described. The results have shown that the transformed 3 nm nanoparticles have a magnetic anisotropy constant that is smaller than those for the bigger particles and the fully ordered [L1.sub.0] bulk phase.

Nanostructured FePt: M (M=C, Ag, Cu) perpendicular magnetic recording media is investigated by numerical simulations and model calculations. The simulations show that intergranular exchange reduces the coercivity of the system, and the magnetization reversal proceeds in a regime between localized nucleation and discrete domain-wall pinning, depending on the intergranular exchange.

A generalized Ruderman-Kittel-Kasuya-Yosida (RKKY) approach is employed to estimate indirect exchange interactions between localized spin in doped magnetic semiconductors. A closed expression with simple geometric interpretation is found in the dilute limit of exchange mediated by two overlapping orbitals.

An attempt is made to examine the structure of micromagnetic energy barriers responsible for slow magnetization processes. Thermally activated slow magnetization processes proceed over energy barriers whose structure is determined by the micromagnetic free energy.

Magnetic properties and L1(sub 0) phase formation of FePt films is investigated by rapid thermal annealing (RTA) and high current-density ion-beam irradiation. The sample prepared by RTA at 550 degree Celsius is found to have (001) texture and strong magnetic perpendicular anisotropy with H(sub c) equal to 6 kOe.

A study of the dependence of magnetic properties in Mn-doped ZnO on sample processing conditions is presented. The ferromagnetism observed at room temperature in the low-temperature-sintered samples is gradually suppressed and finally completely removed, with an increase of annealing temperature.

The high-field spin structure of magnetic perovskites and related magnetoresistive materials is investigated by model calculations. The noncollinear structure, which contributes to the zero-and finite-temperature spin mixing and reduces the magnetorsistance, is strongly field dependent.

The origin and physical nature anisotropic exchange interactions are investigated. The resulting exchange stiffness is anisotropic, even if the interaction is mediated by an isotropic free electron gas.

The potential use of interacting magnetic nanodots for quantum computing (qubit) operations is investigated by model calculations. The results indicated that maximum operation temperature is proportional to the magnetocrystalline anisotropy of the dot material.

The damping of magnetization processes in nanostructures is investigated by Fokker-Planck-type model calculations and quantum-mechanical considerations based on Fermi's golden rule. In the absence of energy barriers, the problem reduces to a magnetic diffusion equation with a particle-size-dependent diffusivity.

An investigation on the Sm-Co/Co hard/ soft multilayers is presented with varying thickness of soft phase layers. The result suggested that the 1min annealing at 525 degree Celsius retains the layer structure unchanged and the hard phase of Sm-Co forms.

Investigations on the structural and magnetic properties of laminated (Nd, Dy)(Fe, Co, Nb, B)(sub 5.5)/alpha-Fe nanocomposites are conducted. The coercivity is found to increase to 1608 kA/m (20.2 kOe) in thermally processed Nd-Dy-Fe-Co-Nb-B(15 nm)/Fe(4 nm) multilayered nanocomposities.

The fabrication of the L1(sub 0)-ordered clusters, location of the clusters after assembly, and the magnetic properties are studied. A scheme is used to assemble FePt L1(sub 0)-ordered clusters through the use of ordered nanopore templates and an external magnetic field.

The Growth and magnetism of FePt:C composites in nanoscale channels was examined. Small cluster size and high coercivity of 29.0 kOe were found in the FePt clusters synthesized with carbon and heat treated at high temperatures.