Jenny M. Vargas

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An overview on magnetic of nanostructured magnetic materials is presented, with particular emphasis on the basic features displayed by granular nanomagnetic solids. Besides a review of the basic concepts and experimental techniques, the role of structural disorder (mainly the distribution of grain sizes), interparticle magnetic interactions and surface(More)
We report interparticle interactions effects on the magnetic structure of the surface region in Fe3O4 nanoparticles. For that, we have studied a desirable system composed by Fe3O4 nanoparticles with (d) = 9.3 nm and a narrow size distribution. These particles present an interesting morphology constituted by a crystalline core and a broad (approximately 50%(More)
Electron spin resonance (ESR) can probe conduction electrons (CE) and local moment (LM) spin systems in different materials. A CE spin resonance (CESR) is observed in metallic systems based on light elements or with enhanced Pauli susceptibility. LM ESR can be seen in compounds with paramagnetic ions and localized d or f electrons. Here we report a(More)
We report an alternative synthesis method and novel magnetic properties of Ni-oxide nanoparticles (NPs). The NPs were prepared by thermal decomposition of nickel phosphine complexes in a high-boiling-point organic solvent. These particles exhibit an interesting morphology constituted by a crystalline core and a broad disordered superficial shell. Our(More)
The Electron Spin Resonance (ESR) of diluted magnetic ions (MI) of Er3+, Yb3+ and Mn2+ in Ag nanoparticles (NPs) is reported. Monodisperse samples of Ag NPs doped with these MI were synthesized by reducing silver nitrate and MI-oxides. This simple method can be extended to all rare-earths. The measurements of the g-values and hyperfine splittings indicates(More)
Morphological, structural and magnetic properties of 4.8 nm iron oxide nanoparticles have been investigated after annealing under inert atmosphere at different temperatures. The as-prepared iron oxide nanoparticles have been synthesized by chemical route from high temperature reaction of Fe(acac)3 solution in presence of oleic acid and oleylamine(More)
Luminescence-tunable multicolored LaF3:xCe3+,xGd3+,yEu3+ (x = 5; y = 1, 5, 10, and 15 mol%) nanoparticles have been synthesized via a low cost polyol method. Powder X-ray diffraction and high-resolution transmission electron microscopy studies confirm the hexagonal phase of the LaF3:xCe3+,xGd3+,yEu3+ nanophosphors with average sizes (oval shape) ranging(More)
This study describes the robustness test of a transmission near-infrared spectroscopic (NIRS) model for prediction of drug concentration in core tablets as part of real-time release testing (RTRt) efforts for a continuous manufacturing process. Seven calibration blend samples were prepared spanning a concentration range from 70 to 130% of the active(More)
A near-infrared (NIR) spectroscopic method was developed for real time analysis of the active pharmaceutical ingredient (API) in blends from a continuous manufacturing process. The sampling and analytical errors of these determinations were estimated through variographic analysis. Thirty-three calibration blends were prepared in laboratory scale equipment(More)
The present work describes the synthesis of iron oxide nanoparticles by thermal decomposition of Fe-precursors in argon and vacuum environments with control over particle size distribution, phase composition and the resulting magnetic properties. The Rietveld refinement analysis of X-ray diffraction data revealed the crystallinity as well the single-phase(More)