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The article informs that colloidal dispersions, particularly of charged particles, are used extensively in technological, commercial, and scientific applications ranging from advanced materials to drug delivery systems, biosensory, and as biomaterials in active glasses and bone supplements. Although liquid-like ordered colloidal suspensions resemble ordinary atomic or molecular fluids in several aspects, there are many differences between colloidal and ordinary fluids. Ordinary fluids display a short-ranged repulsive potential and long-range attraction, which limits the fluid state to a rather narrow density range. Theoretical work on these colloidal systems shows that charged particles in solution in the nanoscale regime influence the system stability by segregating into regions near uncharged colloids. This is indeed the case for systems with high size asymmetry, small spherical colloids as well as large colloidal particles.

The effect of N-doping on the microstructure and magnetic properties of thin Fe layers has been employed to construct all Fe-electrode magnetic tunnel junctions that displayed the tunneling magnetoresistance (TMR) effect. Using low nitrogen doses, a reduction in coercivity was achieved due to grain refinement, without a concurrent decrease in the saturation magnetization of the Fe films caused by the formation of crystalline iron nitride phases. It was demonstrated that this N-induced grain refinement can be applied beneficially to control the switching field of the “free” layer in magnetic trilayer structures. In general the ability to control magnetic softness without reducing saturation magnetization will prove important for incorporating high spin-polarized materials into spin valves and TMR devices. [ABSTRACT FROM AUTHOR]

Electrostatically stabilized aqueous dispersions of nm-sized free lipid A particles at low volume fractions (1.0x10[sup -4]≤∅≤3.5x10[sup -4]) in the presence of 1.0-10.0 mM NaCl (25 °C) have been characterized by static and quasielastic light scattering (QELS) techniques, electron microscopy (SEM and TEM), conductivity measurements, and acid-base titrations. QELS and electron microscopy (&ρmicr;[sub TEM]=8.0± 0.6%) yield similar values for the particle size and particle size distribution (&ρmacr;[sub QELS= 10.9± 0.75 %), whereas conductivity and acid-base titrations estimate surface chemical parameters (dissociation constant, ionizable sites, and Stern capacitance). Effective particle charges were determined by fits of the integral equation calculations of the polydisperse static structure factor, &Smacr;(Q), to the light scattering data. Using the particle properties as determined from these experiments, the polydisperse structure factor, &Smacr;(Q), was calculated as a function of volume fraction, ∅, which was found to be consistent with a &Smacr;(Q) dependence on the number particle density. It can be concluded that, at low volume fractions and low ionic strength, the light scattering data are well represented by a Poisson-Boltzmann model (PBC) of fluid-like ordering of free lipid A in aqueous solution. We find that the light scattering data of this dispersion are best described by a model where only a small fraction of the ionizable phosphate groups is dissociated at neutral pH. Finally, light scattering studies of lipid A dispersions of volume fractions of 3.9 x 10[sup -4] ≤ ∅ ≤ 4.9 x 10[sup -4] indicate the presence of long-range order, resulting in distinct peaks which can be assigned either to a face-centered cubic (fcc) lattice (a = 51.7 nm) or a body-centered cubic (bcc) lattice (a=41.5 nm), respectively. [ABSTRACT FROM AUTHOR]

Presents the results of an investigation by transmission electron microscopy, electron diffraction, x-ray diffraction and x-ray reflectivity of sputter-deposited Co/Si multilayers. Retention of elemental regions in structures with individual layer thicknesses; Occurrence of significant intermixing with alloy formation through differentiation in multilayers below five nanometers.

Magnetic multilayers containing Fe-N layers with bilayer periods of between ~15-84 [Angstrom] and sharp interfaces, are successfully grown using an atomic (free radical) nitrogen beam. The phase composition and microstructure is found to be a function of the initial Fe layer thickness prior to nitrogenation. Generally, higher N content phases are found as the initial Fe layer is reduced. Small grains (~10 nm) are observed in multilayers containing [Alpha]-Fe and [Gamma]-[Fe.sub.4] N phases. In these films, a perpendicular anisotropy is found for a certain thickness of the Fe layers. A stripe domain structure associated with this anisotropy is observed. The origin of this anisotropy may be induced stress caused by lattice mismatch between layers and/or lattice dilation due to N incorporation. Index Terms--Atom source, Fe-N, iron nitride, Magnetic multilayers, perpendicular anisotropy, stripe domains.

This article describes a microstructural and magnetic investigation of the modification of Co/Pt multilayer films by Ar ion irradiation which results in a change of the orientation of the magnetization from perpendicular to the film plane to the in-plane direction. Transmission electron microscopy observation confirms the general structure of the as-deposited samples and correlates with the x-ray reflectivity measurements in showing the eventual mixing of the layers and a large increase in grain size caused by the irradiation. TRIM (transport of ions in matter) calculations show that large numbers of recoils are placed outside the individual layers and in the adjacent layers on irradiation. This signifies considerable roughening of the interfaces and mixing in the multilayer structure. Magnetic measurements and magnetic force microscopy observations confirm the decrease of perpendicular anisotropy and the changes of the magnetization direction from the perpendicular direction to an in-plane direction after irradiation. [ABSTRACT FROM AUTHOR]

Interdiffusion and intermixing have been examined in Fe/Si trilayers prepared with ions of different energies, using the direct ion beam deposition technique. Isotope-pure layers were deposited and spin-polarized neutron reflectivity used to determine the role of Fe diffusion in iron silicide formation. It was found that a nonmagnetic iron silicide was formed that contained Fe from both the top and bottom layers in the trilayer, suggesting complete diffusion across the spacer region. Electron microscopy observations revealed the presence of an iron silicide phase and crystalline interface layers in films prepared with low energy ions (30 eV), while mixed and amorphous-like regions were found at higher ion energies (100 eV). © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This article briefly reports microstructural, electrical transport, and magnetic measurements on Co/Si multilayers which are structurally modified by argon ion irradiation during growth. The periodicity and ferromagnetism of the multilayers is retained at ion energies approaching 400 eV. At and above this energy structural modification results in resputtering and thinning of the film, extensive mixing and a destruction of the periodic layered structure with the formation of nonequilibrium microstructures. The measurements show that the modified film is metallic in character, with the presence of low resistance paths and possible spin glass behavior in an amorphous matrix that surrounds a second microstructural component of mainly superparamagnetic nanoclusters. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A large remanent strain has been normally observed in free-standing float zone-grown Tb[sub 0.3]Dy[sub 0.7]Fe[sub 2] (Terfenol-D) following the application of magnetic field or compressive stress. Such a strain is considered to be composed of two parts, leading to reversible and irreversible domain contributions to the magnetostriction, in which the irreversible part corresponds to the magnetostrictive jump effect belonging to non-180° domain wall motion, and the reversible part contributes to the slower changes of magnetostriction. With no stress applied, the specimen shows a jump field of 21 and 53 Oe for 180° and non-180° domain wall motion, respectively. The jump field, distribution width and hysteresis field for non-180° domain wall motion are all increased with increasing stress, indicating complicated interactions between magnetic domains and defects. Stacking faults are found by electron microscopy to often act as domain-wall pinning centers, and scanning probe microscopy shows specific domain configurations are formed around excess rare earth, twin boundaries, and grain boundaries due to induced stresses and demagnetization effects. The influence of such interactions on magnetostrictive performance is discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which measured the microstructure, magnetic, magnetoelastic behavior of an as-cast samples of the terbium-dysprosium-iron alloy system. Experimental details; Results and discussion; Conclusions.