Jong-Ho Jun

Synthesis and characterization of Ni magnetic nanoparticles in AlMCM41 host

Superparamagnetic nickel nanoparticles were prepared by incorporating nickel ion into AlMCM41 as a nanoreactor and then reduced with sodium borohydride or H2 gas. Products were characterized by elemental analysis, transmission electron microscopy, X-ray powder diffraction, and magnetic susceptibility. The nickel particle size and blocking temperature depend on the reduction method. q 2002 Elsevier Science Ltd. All rights reserved.

A Facile Fabrication of Fe

Monodispersed superparamagnetic magnetite submicron particles were synthesized by using a one-step solvothermal method. Increasing the volume ratio of ethylene glycol/diethylene glycol (EG/DEG) shows a gradual increase in the size of primary nanograin and secondary Fe3O4 submicroparticles. To induce the photo-magnetic functionality, we have successfully synthesized the multifunctional core-shell (Fe3O4/ZnO) submicron particles by atomic layer deposition (ALD) method. Microstructure and magnetic properties of the multifunctional core/shell submicron particles are investigated by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and photoluminescence spectroscopy.

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Abstract The new amorphous intermetallic materials, M3(GaTe3)2 (M = Cr, Fe, Co) are prepared by using a rapid precipitation metathesis reaction between the Zintl phase material K3GaTe3 and the divalent transition metal halides in aqueous solution. The d.c. specific resistivity measurements of these materials exhibit metallic (M = Fe, Co) and semiconductor (M = Cr) behavior. The magnetic and electrical properties for these materials are examined as a function of temperature, Cr3(GaTe3)2 exhibits antiferromagnetic coupling between localized magnetic moments and highly temperature dependent semiconductivity. Two materials undergo a transition to a spin glass state at low temperature (for M = Fe, Tf = 22 K; for M = Co, Tf = 2.2 K). Magnetization data are also reported as both thermal remanent magnetization (TRM) and isothermal remanent magnetization (IRM) as a function of magnetizing field and temperature. At a magnetization field of 1 kG and a temperature of 6 K, the Fe3(GaTe3)2 exhibit a photomagnetic response consistent with a disruption of the spin-glass state that results from a series of pulses of ultraviolet radiation.

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One-dimensional-magnetic nanostructures have recently attracted much attention because of their intriguing properties that are not displayed by their bulk or particle counterparts. One of the commonly used methods for generating ID-nanostructures is based on the electrodeposition of various materials in porous membranes. This technique has been applied to fabricate metallic nanowires as arrays of wires perpendicular to the substrate. They display unique magnetic properties (e.g., anisotropic magnetization). Electrodeposition is, however, of limited use for oxide-based magnetic materials, due to the difficulty involved in the formation of oxides through electrochemical deposition. We obtained zinc ferrite nanowires inside an anodic aluminum oxide (AAO) template using a novel technology fundamentally different from electrodeposition. First, fabricated zinc ferrite nanoparticles were injected in the AAO template and then annealed in air. The process of embedding particles into the pores was assisted by the magnetic field of a permanent magnet placed under the substrate. The physical and chemical properties of these zinc ferrite nanowires have been investigated by thermogravimetric analysis, infrared, X-ray diffraction, scanning electron microscope, and superconducting quantum interference device. The nanoparticles embedded into the pores exhibited superparamagnetic behavior with the blocking temperature of 15 K. After annealing, the particles formed nanowires and the hysteresis of the annealed samples increased significantly.