Monodisperse 4 nm FePt magnetic nanoparticles were synthesized by superhydride reduction of FeCl2 and Pt(acac)2 at high temperature, and thin assemblies of FePt nanoparticles with controlled thickness were formed via polymer mediated self-assembly. Adding superhydride (LiBEt3H) to the phenyl ether solution of FeCl2 and Pt(acac)2 in the presence of oleic acid, oleylamine, and 1,2-hexadecanediol at 200 °C, followed by refluxing at 263 °C, led to monodisperse 4 nm FePt nanoparticles. The initial molar ratio of the metal precursors was retained during the synthesis, and the final FePt composition of the particles was readily tuned. Alternately, adsorbing a layer of polyethylenimine (PEI) and the FePt nanoparticles onto a solid substrate resulted in nanoparticle assemblies with tunable thickness. Chemical analysis of the assemblies revealed that more iron oxide was present in the thinner assemblies annealed at lower temperature or for shorter time. Thermal annealing induced the internal particle structure change from chemically disordered fcc to chemically ordered fct and transformed the thin assembly from superparamagnetic to ferromagnetic. This controlled synthesis and assembly can be used to fabricate FePt nanoparticle-based functional devices for future nanomagnetic applications.

We present a simple polymer-mediated process of assembling magnetic FePt nanoparticles on a solid substrate. Alternatively absorbing the PEI molecule and FePt nanoparticles on a HO-terminated solid surface leads to a smooth FePt nanoparticle assembly with controlled assembly thickness and dimension. Magnetic measurements show that the thermally annealed FePt nanoparticle assembly as thin as three nanoparticle layers is ferromagnetic. The magnetization direction of this thin FePt nanoparticle assembly is readily controlled with the laser-assisted magnetic writing. The reported process can be applied to various substrates, nanoparticles, and functional macromolecules and will be useful for future magnetic nanodevice fabrication.

Previously, ion-beam irradiation has been shown to locally alter the magnetic properties of thin Co/Pt multilayer films. In this work, we have used ion-beam irradiation through a silicon stencil mask having 1-μm-diam holes to pattern a magnetic film. Regularly spaced micrometer-sized regions of magnetically altered material have been produced over areas of a square millimeter in Co/Pt multilayers. These magnetic structures have been observed by magnetic force microscopy. The patterning technique is demonstrated with mask–sample spacing as large as 0.5 mm. In addition, smaller regions of magnetic contrast, down to 100 nm, were created by using two masks with partially overlapping micrometer holes. Such patterned magnetic films are of interest for application in high-density magnetic recording.

The formation of NiSi films from the reaction of Ni2Si with (100) and (111) silicon substrates was found to be controlled by a lattice diffusion process with an activation energy of 1.70 eV. In order to correlate kinetic information obtained by Rutherford backscattering with x-ray diffraction data, ‘‘standard’’ diffraction powder patterns for both Ni2Si and NiSi have been established. The existence of a metastable hexagonal form of NiSi has been confirmed. Observations on the formation of Ni2Si confirm previous investigations. The diffusion process at work during the formation of NiSi is discussed in terms of the crystalline anisotropy of this compound and compared to what is known about diffusion in other silicides.

Co/Pt multilayers can exhibit large perpendicular anisotropies and coercivities that are very sensitive to the quality of the Co/Pt interfaces. We have characterized the dependence of coercivity of Co/Pt multilayers on irradiation with various ion species (He+, Ar+, and Ga+), energies (20 keV–2 MeV), and doses (1011–1017 ions/cm2), in order to understand better the nature of the structural changes responsible for the magnetic changes. We find that, in general, the system is much more sensitive to irradiation than expected on the basis of a nearest-neighbor coupling model and simple ballistic ion-beam mixing.

Shallow (<0.2 μm) n+ layers in Si with high conductivity (<40 Ω/⧠) have been formed by high-dose (2×1016 cm−2) As implants. Experimental observations of As distributions and carrier concentrations are successfully simulated by a computer program which accounts for both the concentration dependent diffusion and As clustering effects. Reduction of electrical carriers in high-dose As implanted Si during moderate temperature (∼800 ° C) heat treatments is readily explained by the kinetics of As clustering. Physical limitations on the conductivity which can be achieved by thermally annealed As implants in Si are also discussed.

Co/Pt multilayer films with perpendicular magnetic anisotropy and large out-of-plane coercivities of 3.9 -8.5 kOe have been found to undergo a spin reorientation transition from out-of-plane to in-plane upon irradiation with 700 keV nitrogen ions. X-ray reflectivity experiments show that the multilayer structure gets progressively disrupted with increasing ion dose, providing direct evidence for local atomic displacements at the Co/Pt interfaces. This effectively destroys the magnetic interface anisotropy, which was varied by about a factor of two, between K S ≅ 0.4 erg/cm 2 and K S ≅ 0.85 erg/cm 2 for two particular films. The dose required to initiate spinreorientation, 6⋅1014 N +

Target presputtering effects on stoichiometry and deposition rate of YBaCuO thin films grown by dc magnetron sputtering Appl. Phys. Lett. 52, 1907Lett. 52, (1988; 10.1063/1.99740 Enhanced CuTeflon adhesion by presputtering treatment: Effect of surface morphology changes