Hossein Akbari

PREVENTION OF SINTERING DURING ANNEALING PROCESS OF FePt NANOPARTICLES COATED WITH ZnO SHELL

Monodispersed 4.1 nm FePt nanoparticles with narrow size distribution were successfully synthesized by the chemical polyol process with co-reduction of Fe(acac)3 and Pt(acac)2 in the presence of 1,2-hexadecanediol as a reducing agent. To achieve hard ferromagnetic behavior with L10 phase and face center tetragonal (fct) structure, high temperature annealing is performed. Annealing causes the surfactant surrounding particles to decompose and agglomeration of particles occurs. In the present work, chemically synthesized FePt nanoparticles were coated with nonmagnetic ZnO oxide shell to prevent them from sintering. Coercivity of FePt and FePt/ZnO nanoparticles increases from 5 kOe to 10 kOe and 1.8 kOe to 6 kOe respectively, with the increasing annealing temperatures from 650 to 750°C.

Structural, Half-Metallic, Optical, and Thermoelectric Study on the Zr 2 TiX (X = Al, Ga, Ge, Si) Heuslers: by DFT

Based on the density functional theory (DFT) framework, the mechanical, half-metallic (HF), optical and thermoelectric properties of Zr2TiX (X = Al, Ga, Ge, Si) Heusler compounds are calculated. The mechanical calculations show good agreement of the lattice constant results with other experiment. The magnetic moments of Zr2TiX (X = Al, Ga, Ge, Si) compounds have been calculated by 1.95, 1.85, 2 and 2.1μB respectively and their stability were founded in the ferromagnetic phase for all cases. The density of states (DOS) indicates splitting states on Fermi level due to Zr d and Ti d overlapping by an asymmetry behavior at two dp and dn spins. The elastic stability, Paugh and Cauchy coefficients imply to the soft and ductility nature of these materials. Also, the optical parameters such as dielectric, refraction, absorption and loss functions have been shown the optical response in the visible area. The thermoelectric treatments indicate good electronic and thermal conductivity with high Seebeck and merit coefficient which is sensitive to the external magnetic moments.