Synthesis and characterization of FePt nanoparticles by high energy ball milling with and without surfactant

FePt nanoparticles were prepared by high energy ball milling (HEBM) in two different ways. In the first one, elemental powders were mixed and milled whereas in the second one the milling was performed in the presence of oleyl amine and oleic acid as surfactants and hexane as a solvent. X-ray diffraction shows that when the milling is performed in dry conditions, Fe and Pt are alloyed after 5 h, whereas in the wet milling procedure alloying does not take place. In the first case, the diffraction pattern corresponds to the disordered FCC phase. This behavior is also corroborated by the evolution of the magnetic characteristics. In the case of the alloy obtained in dry conditions, the powder was heat treated in order to induce the transformation to the ordered phase. Coercivities of 2.5 kOe are obtained after 650 °C for 2 h.

► Fe and Pt powders in the presence of surfactants don’t alloyed by HEBM technique.
► FePt alloys obtained by dry milling exhibit particle sizes of around 10 μm.
► FePt alloys obtained by dry milling exhibit soft magnetic behavior.
► A thermal treatment induces a phase transformation from FCC to FCT.