Of Fept Nanoparticle Films And Annealing The Magnetic Influence

Chemical ordered L10 FePt binary alloy have high potential for extremely high-density magnetic recording media, nanocomposite permanent magnets, because of their large uniaxial magnetocrytalline anisotropy, satisfied mechanical strength, and good chemical stability. In this paper, high-temperature solution-phase conditions were used to synthesize FePt nanoparticles, and the effects of the amount and ration of oleylamine and oleic acid on the size and shape of FePt nanoparticles were investigated. The results showed that the size of as-prepared FePt nanoparticles increased with increasing the amount and ration of leylamine and oleic acid, and the shape of FePt nanoparticles can be tuned from sphere to cube. 4nm spheric FePt nanoparticles were obtained when the ration of oleylamine to oleic acid was 2:2 ; while 10nm cubic FePt nanoparticles were obtained when the ration of oleylamine to oleic acid was 4:4. Moreover, increasing the amount of oleylamine to 4.4 mmol led to cubic FePt with smooth arc rather than with sharp right angle in the corner.Uniform 4nm spheric FePt nanoparticles were obtained by co-reduction method, and FePt films were fabricated by polymer mediated self-assembly. Then FePt films were postannealed by both conventional thermal annealing and rapid thermal annealing.The microstructure and magnetic properties of FePt films annealed by conventional thermal annealing at various temperatures for 30 minutes have been studied. It has been found that the ordering of L10 phase occured at the temperature of 500℃. After annealed at the temperature of 600℃, the ordering parameter S of FePt films was 0.7, and the coercivity was up to 0.55T at room temperature.The influences of different rapid annealing parameters on the microstructure and magnetic properties of FePt films were investigated. The results showed that FePt films annealed at 850℃for 30s showed fct structure and ferromagnetic behaviors; when annealing temperature was above 950℃and annealing time was below 10s, magnetic easy-axis of FePt films was partly perpendicular to the plane. Both X-diffraction patterns and room temperature hysteresis loops showed that FePt films with 12 layers after annealed at 1000℃for 10s has somewhat (001) texture.