Morphological control of FePt nanoparticles has been systematically studied. By varying synthetic parameters including precursors, solvents, amount of surfactants, and heating rate of the solution, the particle size from 2 to 9 nm can be tuned with 1 nm accuracy. While most particles are spherical in shape, cubic particles can be obtained when particles are greater than 7 nm. Rod-shape nanoparticles have also been obtained. The as-synthesized nanoparticles are found to be superparamagnetic at room temperature and their blocking temperature is size dependent that increases with particle size. After annealing in a reducing atmosphere, the nanoparticles form hard magnetic films with ordered fct structure and high coercivity up to 2.7 T.

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Bimagnetic FePt/ Fe 3 O 4 nanoparticles with core/shell or heterodimer structure have been prepared using a sequential synthetic method. The dimension of both FePt and Fe 3 O 4 was tuned by varying the synthesis parameters. The as-synthesized bimagnetic nanoparticles were superparamagnetic at room temperature. After being annealed in a reducing atmosphere, the FePt/ Fe 3 O 4 bimagnetic nanoparticles were converted to a hard magnetic nanocomposite with enhanced energy products due to the exchange coupling between the hard and soft magnetic phases. It was found that the exchange coupling in nanocomposites made from the core/shell nanoparticles is stronger than that from the heterodimer nanoparticles. By tuning the dimensions of the FePt and Fe 3 O 4 phases, the energy product up to 17.8 MGOe was achieved in the annealed nanocomposites, which is 36% higher than the isotropic single-phase FePt counterpart.

FePt nanorods and nanowires have been synthesized by the reduction of Pt(acac)(2) and the thermal decomposition of Fe(CO)(5) in the presence of solvents/surfactants by simply controlling the sequence of addition of surfactants. The as-synthesized FePt nanorods and nanowires have a face centered cubic structure with average diameter of 3 nm. Length of nanorods and nanowires can be adjusted in the range of 15-150 nm by varying reaction parameters. Nanocrystalline L1(0) FePt phase with coercivity up to 24 kOe was obtained after heat treatments.

We report a two-step chemical solution process for synthesis of FePt/Au core/shell nanoparticles. First, FePt nanoparticles were synthesized using a typical polyol process. The as-synthesized FePt nanoparticles were then used as seed materials and were coated with gold shells by reduction of the gold precursors. The coated nanoparticles have been characterized using various structural and morphological measurements to confirm the FePt/Au core/shell morphology. The as-synthesized FePt/Au nanoparticles were found to be superparamagnetic and became ferromagnetic after annealing at 400 °C. The surface modification of FePt/Au core/ shell nanoparticles from hydrophobic to hydrophilic was achieved through ligand exchange to make them water dispersible for potential biomedical applications.

We report a systematic study on rapid thermal annealing ͑RTA͒ of FePt nanoparticles. FePt particles with an average size of 8 nm were synthesized by a chemical solution method, and then annealed using RTA and conventional furnace annealing ͑FA͒. It was observed that FePt nanoparticles can be transformed from disordered A1 phase to ordered L1 0 phase at 650°C for 10 s using RTA, which is much shorter than the time needed for FA. The transmission electron microscopy and x-ray diffraction studies have revealed that the particle agglomeration and grain growth in the RTA treated samples are much less than in the FA treated samples. A linear correlation between the coercivity and the square root of the treatment time ͱ t was observed in the RTA treated samples, which implies that the phase transition is related to atomic diffusion of Fe atoms from Fe-rich shells into the Pt-rich cores.

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The AlGaInP red laser diodes were developed at the end of the 1980s, and since then we have been improving performance of laser diodes. Along with the improvement of laser performance, laser diodes has been used various applications such as optical discs and sensors. Recently, research and practical use of display applications and AR / VR devices are remarkable. In this paper, we mainly report on red laser diodes developed for display applications.