Composition, Size, Structure, and Magnetic Characterization of Iron-Platinum Nano-particles

Iron-platinum (FePt) nano-particles were synthesized using a hot metal salt reduction reaction with iron chloride and platinum acetylacetonate as the precursor salts. The synthesis route was based upon work done previously by Sun et Al .[6]. The size and composition of the FePt nano-particles were controlled by varying the surfactant to reagent molar ratio and refluxing time during synthesis. The average size of FePt nano-particles synthesized ranged from 4.08 nm to 5.23 nm. The composition of the nano-particles ranged from Fe 60 Pt 40 to Fe 55 Pt 45 . The size was shown to increase as the surfactant to reagent molar ratio was changed from 1:6 to 1:1. The platinum composition increased from 40 % to 45 % with an increase in the refluxing time from 30 minutes to 60 minutes. The X-ray analysis (XRD) showed that the unannealed nano-particles had a FCC crystal structure. The FCC FePt nano-particles were superparamagnetic at room temperature. A blocking temperature (T b ) of 35 K was measured for 5.23 nm Fe 55 Pt 45 nano-particles. Annealing of the Fe 55 Pt 45 nano-particles induced a FCT crystal structure with hard-magnetic properties. Coercivity (H c ) of approximately 13000 Oe was measured at room temperature.