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Gold decorated NaYF4:Yb,Er/NaYF4/silica (core/shell/shell) upconversion (UC) nanoparticles (~70–80 nm) were synthesized using tetraethyl orthosilicate and chloroauric acid in a one-step reverse microemulsion method. Gold nanoparticles (~6 nm) were deposited on the surface of silica shell of these core/shell/shell nanoparticles. The total upconversion emission intensity (green, red, and blue) of the core/shell/shell nanoparticles decreased by ~31% after Au was deposited on the surface of silica shell. The upconverted green light was coupled with the surface plasmon of Au leading to rapid heat conversion. These UC/silica/Au nanoparticles were very efficient to destroy BE(2)-C cancer cells and showed strong potential in photothermal therapy.

The effects of L10 CoPt-TiO2/FePt-TiO2 bilayer and (CoxFe100-x)50Pt50-TiO2 (0 ? x ? 100 at.%) multilayer exchange coupled media on switching field and magnetization reversal mechanism were studied. Results showed that both bilayer and multilayer exchange coupled media with out-of-plane anisotropy in the hard and soft layers were effective to reduce the switching field of single layer FePt-TiO2 media. First order reversal curve (FORC) distribution indicated that switching field distribution in the bilayer and multilayer exchanged coupled media was significantly narrowed down compared to the single layer and magnetization reversal was ascribed to domain formation followed by domain wall motion.

The microstructures and magnetic properties of FePtC films grown on MgO/CrRu/glass substrates under different sputtering parameters were systematically investigated. Increased temperature induced chemical ordering and the increase of coercivity. The microstructures of FePtC film showed a two-layer structure with a granular layer above a continuous underlying layer. With increasing sputtering pressure (P??), the intensity of FePt (001) peak initially increased, and then decreased when PAr ? 20 mTorr. At 20 mTorr, Hc value increased to ~9.5 kOe, and only one magnetic layer was observed with increase of PAr ~ 50 mTorr. An increase of sputtering power at high pressures will further improve the magnetic isolation of FePt grains.

A magnetic polymeric carrier, composed of biodegradable poly( d , l -lactide) microspheres, maghemite nanoparticles and anti-cancer drug (paclitaxel) was successfully prepared in dichloromethane using high-speed homogenization. Maghemite nanoparticles were well dispersed in PLA matrix. The carrier was magnetically responsive and exhibited low cytotoxicity. Release of loaded paclitaxel was enhanced by applying an oscillating magnetic field. The thermal energy generated by maghemite nanoparticles due to magnetic hysteresis loss was very low and considered negligible in influencing the release behavior. Alternating movement of the nanoparticles, stimulated by magnetic force, resulting in deterioration of the mechanical properties of polymer matrix was likely to be the main reason for the enhancement in drug release.

Amorphous silica shells, used for functionalization of inorganic nanoparticles in bioapplications, were coated on chemically synthesized NaYF4:Yb,Er upconversion fluorescent nanoparticles via a reverse microemulsion method by using dual surfactants of polyoxyethylene (5) nonylphenylether and 1-hexanol, and tetraethyl orthosilicate as precursor. NaYF4:Yb,Er nanoparticles were equiaxed with a particle size of 11.1 ± 1.3 nm. The thickness of silica shell was ∼8 nm. NaYF4:Yb,Er/silica core/shell nanoparticles were well dispersed in solvents such as ethanol and deionized water. The emission intensities of NaYF4:Yb,Er/silica core/shell nanoparticles remained the same as that of uncoated nanoparticles after surface functionalization with an amine group using (3-aminopropyl)-trimethoxysilan. Silica, although providing a good barrier to the nonradiative relaxation between the upconversion nanoparticles and the environments, did not enhance the emission intensity of upconversion nanoparticles. To increase the emission intensity of NaYF4:Yb,Er/silica core/shell nanoparticles, an undoped NaYF4 shell (∼3-nm thick) was deposited on the upconversion nanoparticles before the silica coating. The total emission intensity of NaYF4:Yb,Er/NaYF4/silica core/shell/shell nanoparticles increased by 15 times compared to that without the intermediate NaYF4 shell. The critical shell thickness of NaYF4 was ∼3 nm, beyond which no further emission intensity enhancement was observed.

Nickel ferrite nanoparticles with or without oleic acid surface coating were mixed with poly(D,L-lactide) (PLA) by double emulsion method. If the nanoparticles were prepared without oleic acid coating, they adsorbed on the PLA surface. If the nanoparticles were coated with oleic acid, they could be readily encapsulated within the PLA microspheres. A slight depression in glass transition temperature was found in all composites and it could be related to the interfacial energies between nanoparticles and PLA. Optimum mixed composite was achieved by reducing interfacial energy. However, loading capacity was limited in this composite. Increasing the amount of nickel ferrite nanoparticles was not useful to increase loading capacity. Cytotoxicity of the composite decreased significantly when nickel ferrite nanoparticles were effectively encapsulated in PLA microspheres.

This work focuses on the magnetism-control study of nickel (Ni) nanoparticles (NPs) with non-magnetic cores of noble metals (M = Ag, Au). Monodispersed M NPs used as templates were synthesized by reducing their salt with a weak reductant—oleylamine (OA). The OA acted as surfactant and non-coordinating reagent in the preparation of Ni NPs with a narrow size distribution. Then Ni atoms were controlled to grow upon the M NPs by controlling the decomposition of nickel acetylacetonate in OA. The as-prepared M and core/shell M/Ni NPs exhibit spherical shape, as characterized by transmission electron microscopy. The systematic study indicated that the Ni shell exhibits face-centered cubic crystal structure and is relatively stable in air. The hydrophobic OA molecules on the surface could be exchanged by hydrophilic imidazole to make the samples water-soluble. Magnetic study of core/shell NPs indicated that their blocking temperatures could be tuned by modulating either core size or shell thickness. The novel mag...

The effects of interface roughness of Ta seedlayer on the structural and magnetic properties of Co 72 Pt 28 (20 nm)/Ru(30 nm)/Pt(2 nm)/Ta(5 nm)/glass were investigated. Uniaxial perpendicular magnetic anisotropy (8.6×10 6 ergs/cc), coercivity (5.5 kOe) and nucleation field (−2.8 kOe) in the Co 72 Pt 28 thin film sputter-deposited on relatively smooth surface of Ta seedlayer were achieved. The results showed that relatively smoother interface roughness of Ta seedlayer improved the CoPt/Ru (0 0 0 2) texture and magnetic properties.

Bulk NaYF4:Yb,Er particles (∼1.4 μm particle size) were synthesized using a hydrothermal method. As-synthesized particles were subsequently ball milled to three average particle sizes, namely, ∼260 nm, 160 nm, and 100 nm. The x-ray diffraction pattern showed an hcp phase for as-synthesized and ball-milled particles with a predominant (100) peak. Room temperature emission spectra showed no size dependent peak shifts or peak broadening. The intensities of both green and red emissions decreased with increasing milling time. Segregation of Er ions was detected on the surfaces of milled particle that reduced the sensitizer-activator transition probability, resulting in decreased emission intensities. The green-to-red emission ratio was correlated to the surface enrichment of Er, which affected the cross-relaxation of luminescence dynamics.

Near infrared (NIR) absorbing Au-Au(2)S nanoparticles were modified with surfactants of different hydrocarbon chain lengths to allow loading of anticancer drug, cisplatin. The interfacial interactions and surfactant chain length effects on drug loading, optical properties and cytotoxicity were discussed in this work. Short-chain surfactants were oriented closer to the surface normal and were adsorbed at higher densities. Surface modification also changed the optical properties of the particles. Notably, particles modified with short-chain surfactants exhibited a red shift, whereas particles modified with long-chain surfactants showed a blue shift. The in vitro cytotoxicity of drug-loaded surface-modified particles was dependent on the surfactants' chain length. Significant cytotoxicity was observed for 1 mg/ml of drug-loaded particles using surfactants with the shortest chain length. After NIR triggered drug release, the released Pt compounds were observed to be cytotoxic, while remaining nanoparticles did not exhibit any cytotoxicity. Also, the released Pt compounds upon NIR irradiation of drug-loaded particles were observed to be more toxic and had a different molecular structure from cisplatin.

Core–shell Ni–Fe@ferrite nanoparticles with an average diameter of 14 nm and shell thickness of 3 nm were synthesized through a redox-transmetalation process. The alloy core and spinel oxide shell were verified by X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy. The hydrophobic oleylamine molecules on the surface were replaced by hydrophilic meso -2,3-Dimercaptosuccinic acid to make the nanoparticles to be water-soluble. X-ray diffraction study of the as-prepared core–shell nanoparticles indicates that they remained face centered cubic alloy core and spinel shell form in air. Magnetic measurements indicate that the core–shell nanoparticles exhibit superparamagnetic and exchange bias characteristics at 300 K and 5 K, respectively.

The FePt:C films with different volume fractions of carbon were epitaxially grown on the CrRu(200) underlayer with Pt and MgO intermediate layers. The magnetic properties and microstructure of these FePt:C films were investigated. The FePt:C films grown on Pt intermediate layer consisted of a continuous layer of FePt, with overlying granular FePt grains. The FePt:C films grown on MgO intermediate layer consisted of a granular FePt:C layer with overlying granular grains. The formation of the overlying granular FePt grains was attributed to carbon diffusion to the surface, which resulted in the second nucleation of FePt. The different interface energy and surface energy of FePt on Pt and MgO intermediate layers caused the formation of initial continuous FePt layer on Pt intermediate layer and initial granular FePt layers on MgO intermediate layer. The out-of-plane coercivity measured at room temperature increased from 10.2 to 19 kOe when C concentrations increased from 0 to 15%. Further increasing the C contents to 20% and 25% caused the decrease of coercivity to 17.2 and 14.8 kOe, respectively. The coercivity of the exchange coupling assisted FePt:C perpendicular media was indeed substantially reduced.

Multistep colloidal chemical routes were employed to synthesize Pt/Au, Pt/iron oxide (IO), and Au/Pt/IO hybrid nanoparticles (NPs). The starting templates, Pt NPs, were synthesized by controlling the decomposition kinetics of platinum acetylacetonate in oleylamine. The morphologies of binary metal Pt/Au hybrid NPs were modulated by controllable attachment of Au nanoscale domains to Pt templates. Similarly, Pt/IO and Au/Pt/IO hybrid NPs were fabricated by the controllable attachment of Fe to the Pt or Pt/Au template NPs. The noble metal domains of as-prepared hybrid NPs had face center cubic crystal structures and did not alloy, as verified by high resolution transmission electron microscopy and X-ray diffraction spectrometry. X-ray diffraction spectrometry study indicates that the IO domains in the as-prepared NPs have a spinel structure. UV−vis study of binary metal Pt/Au hybrid NPs revealed that they have a characteristic plasmon resonance around 525 nm, while dumbbell-like Au/Pt/IO NPs had a plasmon resonance around 600 nm. Furthermore, magnetism study of the binary Pt−IO NPs clearly indicated that the interfacial interactions between Pt and IO domains could result in a shift of the blocking temperature.

Nickel ferrite nanostructured particles coated with chemisorbed oleic acid were successfully synthesized by nonhydrolytic sol-gel method. By varying the composition of metal precursors, two microstructures were obtained, i.e., dispersed nanocrystals (9.7 ± 1.8 nm) and submicron aggregates (152 ± 21 nm) consisted of many nanocrystals (8.1 ± 1.3 nm). Because oleic acid could form complex with iron (III) ions, but not with nickel (II), increasing the concentration of iron precursor consumed more oleic acid and led to insufficient oleic acid coating on particle surface. Strong intercrystallite interaction was induced from less protected nanocrystals, and aggregation thus occurred between different crystallites.

Cisplatin is one of the most effective cytotoxic agents against cancers. Its usage, however, is limited because of severe resistance and systemic toxicity. A formulation of cisplatin-loaded Au–Au2S nanoparticles (NPs) with near-IR (NIR) sensitivity is reported to partly overcome this limitation in this paper. NIR sensitive Au–Au2S NPs were successfully synthesized by the reduction of tetrachloroauric acid (HAuCl4) using sodium sulfide (Na2S), and cisplatin was loaded onto Au–Au2S NPs via a MUA (11-mercaptoundecanoic acid) layer. To further investigate the biological safety of cisplatin-loaded Au–Au2S NPs, three different cell lines were used to investigate the acute cytotoxicity and the long-term potential carcinogenicity in vitro. Cisplatin-loaded Au–Au2S NPs were also tested for limited hemocompatibility in vitro. Our in vitro short and long-term data provided preliminary evidence suggesting that cisplatin-loaded Au–Au2S NPs with NIR sensitivity are nontoxic below the maximum recommended dosage. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008

Near-infrared (NIR)-absorbing nanoparticles synthesized by the reduction of tetrachloroauric acid (HAuCl4) using sodium sulfide (Na2S) exhibited absorption bands at ∼530 nm and at the NIR region of 650−1100 nm. A detailed study on the structure and microstructure of as-synthesized nanoparticles was reported previously. The as-synthesized nanoparticles were found to consist of amorphous AuxS (x = ∼2), mostly well mixed within crystalline Au. In this work, the optical properties were tailored by varying the precursor molar ratios of HAuCl4 and Na2S. In addition, a detailed study of composition and particle-size effects on the optical properties was discussed. The change of polarizability by the introduction of S in the form of AuxS (x = ∼2) had a significant effect on NIR absorption. Also, it was found in this work that exposure of these particles to NIR irradiation using a Nd:YAG laser resulted in loss of the NIR absorption band. Thermal effects generated during NIR irradiation had led to microstructural changes that modified the optical properties of particles.

The infuence of ultrathin nonmagnetic Ag layers on the formation of the ordered fct-L10 PtFe phase and their magnetic properties have been studied, when the thin FePt .lms were deposited on MgO (100) single-crystal substrates. Epitaxial growth of the FePt (001) .lms was observed at the deposition temperature of 400 °C. With ultrathin Ag intermediate layers deposited between FePt layers, the surface morphology changed from the interconnection network to isolated-island character. The perpendicular coercivity of the FePt .lm dramatically increased from 6.5 to 32.5 kOe. The formation mechanism of the isolated island morphology of FePt thin .lms is discussed.

We successfully synthesized near infrared (NIR) sensitive Au(shell)-Au2S(core) nanoparticles, where Au2S dielectric core was encapsulated by a thin gold shell. The cytotoxicity in vitro and biodistribution in vivo of Au-Au2S nanoparticles was studied by using NIH3T3 cells and KM mice, respectively. The quantitative analysis of Au in each tissue of mice was done by using the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Au-Au2S nanoparticles (< 300 μg/ml) showed good biocompatibility. Au-Au2S nanoparticles were preferentially taken up by the liver and spleen, and ultimately eliminated mostly in the feces.

Strain engineering is an effective way to modify functional properties of thin films. Recently, the importance of octahedral rotations in pervoskite films has been recognized in discovering and designing new functional phases. Octahedral behavior of SrRuO3 film as a popular electrode in heterostructured devices is of particular interest for its probable interfacial coupling of octahedra with the functional overlayers. Here we report the strain engineering of octahedral rotations and physical properties that has been achieved in SrRuO3 films in response to the substrate-induced misfit strains of almost the same amplitude but of opposite signs. It shows that the compressively strained film on NdGaO3 substrate displays a rotation pattern of a tetragonal phase whilst the tensilely strained film on KTaO3 substrate has the rotation pattern of the bulk orthorhombic SrRuO3 phase. In addition, the compressively strained film displays a perpendicular magnetic anisotropy while the tensilely strained film has the magnetic easy axis lying in the film plane. The results show the prospect of strain engineered octahedral architecture in producing desired property and novel functionality in the class of perovskite material.

The electric-field control of magnetic properties of $\mathrm{P}{\mathrm{r}}_{0.67}\mathrm{S}{\mathrm{r}}_{0.33}\mathrm{Mn}{\mathrm{O}}_{3}$ (PSMO) film on piezoelectric $\mathrm{Pb}(\mathrm{M}{\mathrm{g}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}){\mathrm{O}}_{3}\ensuremath{-}\mathrm{PbTi}{\mathrm{O}}_{3}$ (PMNT) substrate was investigated. The piezoelectric response of the PMNT substrate to the electric field produced strain that was coupled to the PSMO film. The in-plane compressive (tensile) strain increased (decreased) the magnetization. The change of magnetic moment was associated with the Mn ions. First-principles simulations showed that the strain-induced electronic redistribution of the two ${\mathbit{e}}_{g}$ orbitals $(3{d}_{z}^{2}$ and $3{d}_{{x}^{2}\ensuremath{-}{y}^{2}})$ of Mn ions was responsible for the change of magnetic moment. This work demonstrates that the magnetoelectric effect in manganite/piezoelectric heterostructures originates from the change in ${\mathbit{e}}_{g}$ orbital occupancy of Mn ions induced by strain rather than the interfacial effect.

The long-range order and the extent of crystallization of nanostructured thin films may not be reliably obtained by conventional X-ray diffraction when the crystalline domain size is smaller than the X-ray coherent length. Here we report an investigation of the effects of annealing on Co–C thin films by X-ray absorption spectroscopy. The local atomic order of Co increased with increasing annealing temperature, resulting in the increase of coercivity and saturation magnetization. The Co–C films annealed at 400 °C dominated by hexagonal close-packed phase with optimized magnetic properties are a promising media candidate for high density magnetic recording.

A method based on strain-induced phase transformation was used to lower the ordering temperature of FePt films. The strain resulted from the lattice mismatch between the FePt film and the substrate or underlayer favored the ordering. The relationships between the lattice mismatch, the ordering of FePt film, and the corresponding magnetic anisotropic constant were investigated. A critical lattice mismatch near 6.33% was believed to be most suitable for improving the chemical ordering of the FePt films. CrX (X=Ru, Mo, W, Ti) alloys with (2 0 0) texture was used to control the easy axis and ordering temperature of FePt films on glass substrate. Large uniaxial anisotropy constant K u ⩾1×10 7 erg/cm 3 , good magnetic squareness (∼1) and FePt(0 0 1) texture (rocking curve −5°) were obtained at the temperature T s ⩾250 °C when using CrRu underlayer. The diffusion from overlying layers of Ag and Cu and an inserted Ag pinning layer were effective in reducing the exchange decoupling and changing the magnetization reversal. The media noise was effectively reduced and the SNR was remarkably enhanced when a 2 nm Ag was inserted.

The field dependence of spin and orbital magnetic moments of Fe in L10 FePt magnetic thin films was investigated using X-ray magnetic circular dichroism (XMCD). The spin and orbital moments were calculated using the sum rules; it was found that the spin and orbital moment of Fe in L10 FePt films are ∼2.5 and 0.2 μB, respectively. The relative XMCD asymmetry at Fe L3 peak on the dependence of applied field suggested that the majority magnetic moment of L10 FePt films resulted from Fe.

Monodisperse Au-silicate nanoparticles (10.7±1.6 nm in diameter) were prepared by reduction of aqueous solution containing 2 mM HAuCl4 with sodium citrate (1 wt.%) in a hydrosol, in which small clusters of silicate formed by hydrolysis and polymerization of 3-aminopropyltrimethoxysilane (APTMS). APTMS covalently linked to reduced gold particles through its -NH2 end-group. UV-vis spectra of the obtained Au-silicate nanoparticles showed a peak at ∼690 nm due to the interface effects between the Au and the silicate matrix. The Au-silicate nanoparticles exhibited near-IR (NIR) sensitivity. Cytotoxicity and limited hemocompatibility in vitro for the prepared Au-silicate nanoparticles were also investigated. It was shown that at lower concentration (

Nanocluster beam technology combined with conventional sputtering was used to fabricate FePt–SiO2 nanocomposite films in this present work. The post-deposition annealing affected the final particle size and size distribution of FePt nanoclusters. The effects of both volume fraction of SiO2 matrix and annealing temperature on magnetic and microstructural properties were studied. Partial ordering, grain growth and agglomeration of FePt particles in FePt–SiO2 nanocomposite films occurred during annealing. A higher volume fraction of SiO2 matrix was effective in suppressing diffusion of atoms and magnetic exchange coupling of FePt grains. Excessive SiO2 however resulted in a lower degree of FePt ordering and thus lower coercivity.

FePt nanoparticles produced by condensation of sputtered atoms in a nanocluster beam source at different forming temperatures were investigated using transmission electron microscopy (TEM). At the temperature of 170 K, the particles were icosahedron and the mean particle size was 4 nm with a standard deviation of 16%. At 100 K polygonal shapes of particles with size 5–15 nm such as triangular, square, rhombic, pentagonal, hexagonal, octagonal, and irregular were observed. The three-dimensional (3-D) shapes of the 2-D TEM projections were derived from high resolution, bright field, dark field and weak beam dark field (WBDF) imaging and electron diffraction pattern. The polygonal shapes arose from octahedron, truncated octahedron, cubooctahedra, truncated tetrahedron, triangular platelet, Marks decahedron and icosahedron. The final growth structures did not necessarily have the lowest free energy, but was the one that corresponded to a local minimum governed by specific growth kinetics.

The binding affinity of single stranded DNA (ssDNA) for Au nanoparticles was found to be strongly size dependent. The data clearly indicate that the interaction is not due to a charge screening effect. The smaller particles (5 nm) showed the most pronounced effect and inhibited the hybridization of complementary DNA sequences adsorbed on the Au nanoparticle surface. An experimental procedure was subsequently developed to allow the assembly of 17 and 5 nm gold nanoparticles using only single stranded DNA without the need for DNA hybridization. The assembly was confirmed by transmission electron microscopy (TEM). A potential pitfall in using DNA melting point analysis to infer metal nanoparticle assembly by DNA hybridization was also discovered during the development of this experimental procedure.

The non-specific interaction between single stranded DNA (ssDNA) and 12 nm Pt nanoparticles is investigated in this work. The data show a strong and non-specific interaction between the two which can be exploited for the stabilization of Pt nanoparticles in aqueous solutions. Based on the experimental findings, a non-hybridization based protocol to assemble 17 nm Au and Pt nanoparticles (12 nm cubic and 3.6 nm spherical) by single-stranded DNA was developed. Transmission electron microscopy (TEM) and UV–visible spectroscopy confirmed that Au and Pt nanoparticles could be assembled by the non-specific interaction in an orderly manner. The experimental results also caution against the potential pitfalls in using DNA melting point analysis to infer metal nanoparticle assembly by DNA hybridization.

The safety and toxicity of nanoparticles are of growing concern despite their significant scientific interests and promising potentials in many applications. The properties of nanoparticles depend not only on the size but also the structure, microstructure and surface coating. These in turn are controlled by the synthesis and processing conditions. The dependence of cytotoxicity on particle size and on the presence of oleic acid as surfactant on nickel ferrite particles were investigated in vitro using the Neuro-2A cell line as a model. For nickel ferrite particles without oleic acid prepared by ball milling, cytotoxicity was independent of particle size within the given mass concentrations and surface areas accessible to the cells. For nickel ferrite particles coated with oleic acid prepared by the polyol method, the cytotoxicity significantly increased when one or two layers of oleic acid were deposited. Large particles (150+/-50 nm diameter) showed a higher cytotoxicity than smaller particles (10+/-3 nm diameter).

Au/BaTiO3 nanocomposite thin films with different Au concentrations were prepared by a sol–gel process. The films were characterized using X-ray diffraction, thermal analyses, X-ray absorption spectroscopy, UV-vis spectroscopy, and transmission electron microscopy. The effects of Au concentration and annealing temperature on the structural and optical properties of composite films were investigated. Gold doping lowered the crystallization temperature of as-synthesized amorphous BaTiO3 and enhanced its crystallinity in post-deposition annealing. The Au–BaTiO3 interface was also investigated and no alloying occurred between Au and BaTiO3. The evolution of Au surface plasmon resonance spectra with increasing annealing temperature was observed in the 10 mol% Au/BaTiO3 thin films. The variations of band-gap energy for Au/BaTiO3 films were also discussed.

The surface composition of nanoparticles is generally different from the average or bulk composition; this phenomenon is commonly referred to as surface segregation. In the present work, the surface segregation in Au-Ti nanoparticles has been analyzed based on a thermodynamic model that incorporates the size effect into the quasichemical model. The calculated surface compositions of Au-Ti nanoparticles are compared with that of the bulk Au-Ti alloys.

An analysis of surface segregation of Au-Ti alloy nanoparticle (atomic ratio 1:1) is carried out using Monte Carlo simulation with the energetics described by Bozzolo-Ferrante-Smith method. The surface compositions of Au in Au-Ti nanoparticles are calculated based on the simulation that takes into account the size effect. The segregated surface compositions of Au in the Au-Ti binary alloy single-crystal nanoparticles (with particle diameter of 10-100 nm) are observed to be larger than that of the corresponding bulk single crystal (with the particle diameter > 100 nm). The details of Monte Carlo simulation and the calculated surface compositions due to segregation are discussed.

A new approach to prepare surface-functionalized magnetic nanoparticles by synthesis of poly(methacrylic acid) (PMAA) coated maghemite nanoparticles in aqueous solution is reported. Maghemite (γ-Fe2O3) nanoparticles with an average diameter of 8 ± 2 nm were fabricated and subsequently coated with PMAA by emulsion polymerization. The FTIR study and thermal analysis confirmed the chemical adsorption of methacrylic acid on the maghemite nanoparticle surface, and suggested a symmetrical carboxylate bonding. The free carboxyl group of PMAA, which was verified by FTIR spectroscopy and zeta potential measurement, provided the site for immobilization of foreign molecules. The PMAA coated maghemite nanoparticles were demonstrated as potential magnetically targeted drug carriers by adsorbing an anti-cancer drug (carboplatin) via the ion–dipole interaction between CO2− of PMAA and carboplatin.

Near IR (NIR) sensitive Au–Au2S nanocolloids were prepared by mixing HAuCl4 and Na2S in aqueous solutions. An anti-tumor drug, cis-platin, was adsorbed onto Au–Au2S nanoparticle surface via the 11-mercaptoundecanoic acid (MUA) layers. The results show that the degree of adsorption of cis-platin onto Au–Au2S nanoparticles was controlled by the solution pH value, and the drug release was sensitive to near-infrared irradiation. The cis-platin-loaded Au–Au2S nanocolloids can be potentially applied as NIR activated drug delivery carrier.

The CoCrPt/Ti/NiP films for perpendicular magnetic recording were studied using X-ray scattering and anomalous X-ray scattering. When the NiP seed layer was used, the long range order of the texture peak of the magnetic film decreased and less Co was associated with this Bragg order. The structural results were consistent with the observed increased coercivity and decreased magnetization due to the increased magnetic grain isolation caused by the presence of NiP seed layer.

Iron-nickel-based powders and thin films were synthesized by an electroless polyol method. The growth process as a function of deposition time was studied. The Fe concentration of deposited films and precipitated powders were similar and independent of deposition time. The metalorganic intermediates were present in powders and their amount decreased with time. The morphological investigations suggested that 60 min was the optimum deposition time to deposit dense films with particles of narrow size distribution. In addition, the films deposited at 60 min also possessed the highest saturation magnetization due to a more ordered atomic environment of nickel. The as-deposited Fe was apparently oxidized in the films.

Thermodynamic analysis of a Ni–Co alloy nanoparticle (atomic ratio 1:1) is carried out to study the influence of size effect on surface compositional segregation. The surface compositions of Ni–Co nanoparticles are calculated based on the regular solution model, which takes into account of the size effect, and compared with that of bulk alloy particles with a larger size. It is observed that the segregated surface compositions in the Ni–Co binary alloy single-crystal nanoparticles (with particle diameter of 10–100 nm) are few times larger than that of the corresponding bulk single crystal (with the particle diameter >100 nm). The details of the thermodynamic modeling and the calculated surface compositions due to segregation are discussed.

An atomistic model based on a classical spin Hamiltonian and a Landau-Lifshitz-Gilbert (LLG) equation was utilized to simulate and gain understanding of the magnetic, interfacial, and reversal properties of perpendicular anisotropy L10-FePt/Ag/L10-FePt pseudo spin valves, with different interfacial roughness, representing the experimentally observed behavior of the interface where the Ag spacer layer was postannealed at different temperatures. Simulation results showed that the influence of the Ag spacer on the independent switching of the FePt layers became stronger with a greater degree of interlayer mixing under higher temperature treatment. This was the result of an increased magnetic polarization of Ag with a decrease in Ag spacer thickness. Furthermore, with greater intermixing the magnetization reversal of the harder fixed FePt layer also changed from a coherent reversal process to one which took place via nucleation and propagation of reversed domains.

FePt films on PZN-PT single-crystal substrate, the ferromagnetic/piezoelectric (FM/PE) heterostructures, were fabricated by magnetron sputtering. The effects of the electric field on the coercivity and magnetization of the FePt at room temperature in FM/PE heterostructures were investigated. The as-grown FePt film showed an in-plane magnetic anisotropy. Upon applying an electric field, the out-of-plane magnetic loops of the heterostructure changed obviously, but the in-plane loops remained unchanged. When the applied E field increased from 0 to 5 kV/cm, the coercivity of out-of-plane increased from 4614 to 4907 Oe. The change of out-of-plane coercivity with different E field is consistent with the strain-electric-field loop of piezoelectric materials. Therefore, the increase of the coercivity can be attributed to that the electric-field-induced strain resulted in increased anisotropy normal to the film plane. The magnetization reversal process of easy direction was mainly due to domain wall motion, which may explain the invariability of the in-plane loops. Based on these results, it was believed that the electric-field-induced piezoelectric strain from the bottom PZN-PT substrate was effectively transferred to the top FePt layer.

Perpendicular magnetic anisotropy L1 0 -FePt/MgO/[Co/Pd] 30 magnetic tunnel junctions (MTJs) with ultra-thin L1 0 -FePt layer of thickness 1 to 4 nm were fabricated and studied. The ultra-thin L1 0 -FePt behaved as the free layer while the thicker and harder [Co/Pd] 30 behaved as the fixed layer. The interlayer coupling within the MTJ with L1 0 -FePt layer thickness of 4 nm was attributed mainly to magnetostatic coupling and direct coupling due to pinholes. The magnitude of the interlayer coupling field in the L1 0 -FePt/MgO/[Co/Pd] 30 MTJ was insignificant compared to the L1 0 -FePt based pseudo spin valves reported earlier. There was also no sign of dipolar stray field coupling, owing to the single domain characteristic property of the fixed [Co/Pd] 30 layer.

The effects of TiN-ZrO₂ intermediate layer on the microstructures and magnetic properties of FePt films were investigated. The TiN-ZrO2 intermediate layer was granular consisting of grains of solid solution of Ti(Zr)ON segregated by amorphous ZrO₂. By doping ZrO₂ into TiN intermediate layer, the FePt grains became better isolated from each other and the FePt grain size was reduced. For 20 vol. % ZrO₂ doping into TiN, the grain size decreased dramatically from 11. 2 nm to 6. 4 nm, and good perpendicular anisotropy was achieved simultaneously. For the FePt 4nm-SiO₂ 35 vol. % -C 20 vol. % films grown on top of the TiN-ZrO₂ 20 vol. % intermediate layer, well isolated FePt (001) granular films with coercivity higher than 18. 1 kOe and an average size as small as 6. 4 nm were achieved.

Strain-modulated anisotropic electronic charge transfers in perovskite ${\mathrm{Pr}}_{0.67}$${\mathrm{Sr}}_{0.33}$${\mathrm{MnO}}_{3}$ thin films were investigated using polarization dependent x-ray absorption near-edge structure at the Mn $K$ absorption edge and half-integer diffraction. The strain from the lattice mismatch between the film and the substrate affects the ${\mathrm{MnO}}_{6}$ octahedron tilt pattern in thin films, which modifies the Mn-O bond length and bond angles, and charge transfer properties. The probability of charge transfer from O to Mn is anisotropic along the in-plane and out-of-plane directions, which is enhanced in the direction with compressive strain due to a larger overlap of Mn 3$d$ and O 2$p$ orbitals as a result of a shorter Mn-O bond length. These results were further verified using the ab initio FEFF calculations and Curie temperature calculation.

X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are two main x-ray techniques in synchrotron radiation facilities. In this Note, we present an experimental setup capable of performing simultaneous XRD and XAS measurements by the application of a pixel-array area detector. For XRD, the momentum transfer in specular diffraction was measured by scanning the X-ray energy with fixed incoming and outgoing x-ray angles. By selecting a small fixed region of the detector to collect the XRD signal, the rest of the area was available for collecting the x-ray fluorescence for XAS measurements. The simultaneous measurement of XRD and X-ray absorption near edge structure for Pr0.67Sr0.33MnO3 film was demonstrated as a proof of principle for future time-resolved pump-probe measurements. A static sample makes it easy to maintain an accurate overlap of the X-ray spot and laser pump beam.

The effect of NiP seed layer on CoCrPt perpendicular recording media has been studied. It was observed that the well isolated, small cluster of amorphous NiP layer helped to reduce the grain size, and the grain size distribution of the CoCrPt magnetic layer. The improvement in grain size and distribution also lead to better magnetic and recording properties.

A non-aqueous, electroless, polyol process was used to deposit nanostructured NixCo100−x films on Cu substrates by reducing nickel acetate and cobalt acetate in refluxing ethylene glycol at 194°C for 1 h. As-deposited films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), microhardness and microscratch tests. The films had a (1 1 1) texture and the average crystallite size increased with x from 15 to 64 nm. The films showed in-plane magnetization anisotropy. Saturation magnetization (Ms) increased with increasing Co concentration and reached 1421 emu/cm3 for Co100. The perpendicular coercivity (Hc⊥) was higher than that in-plane (Hc). The Ni50Co50 film had the highest Hc⊥ and microhardness compared to other films of different compositions. The critical load for delamination increased with x and was independent of film thickness. In this polyol process film deposition on the substrate competed with undesirable powder precipitation in the solution. Lowering the reaction temperature did not favor film deposition. However, film deposition occurred when an electric field was applied during the reaction at temperature as low as 100°C. Precipitation of colloidal particles persisted at this low temperature in a different diol.

A number of high-frequency microwave sintering studies of alumina have reported that sintering proceeds much faster in microwave furnaces when compared to conventional furnaces, and that densification can occur at lower temperatures. These differences have motivated the search for a nonthermal microwave enhancement effect such as the time-averaged microwave field-induced mass transport effect proposed by Rybakov and Semenov (1994). To assess the difference between microwave and conventional sintering, and the presence of a nonthermal effect in microwave sintering, a study of millimeter-wave (mm-wave) (35 GHz) sintering has been conducted at the Naval Research Laboratory (NRL) using a well-studied fine-grained (submicron) commercial alumina with reproducibly manufactured properties, Sumitomo AKP-50. This paper reports our results, which generally indicate no large differences in the required temperatures for densification of conventionally and microwave sintered compacts, or between the resulting microstructures. The nonthermal effect proposed by Ryakov and Semenov was evaluated for fine-grained alumina and found to be small compared to the surface energy driving force for sintering.