Transformation to L1₀ structure in FePd nanoparticles synthesized by modified polyol process

FePd nanoparticles were prepared by the modified polyol process, i.e. simultaneous reduction of palladium acetylacetonate and thermal decomposition of iron pentacarbonyl in a solvent. The well-dispersed FePd particles, with the average particle size of ∼8.4 nm, were obtained using diphenyl ether as a solvent. The structure of FePd nanoparticles transformed to L1₀ structure from face centered cubic (fcc) structure after annealing at 600 °C for 1 h in vacuum. The coercivity of the ordered FePd nanoparticles increased to ∼2 kOe at 5 K from ∼0.6 kOe in the fcc as-made FePd nanoparticle. On the other hand, FePd nanoparticles, synthesized based on the conventional modified polyol process using dioctyl ether as a solvent, showed no structural transformation after annealing up to 700 °C. This is explained in terms of the interruption of thermal diffusion of Fe and Pd atoms during the thermal treatment due to the mixture of interstitial carbon impurity in the synthesis process using dioctyl ether as a solvent.