Synthesis of magnetic nanocomposites and alloys from platinum–iron oxide core–shellnanoparticles

Abstract

This paper presents a systematic study on the generation of ironplatinum-containing magnetic nanocomposites and alloys fromPt@Fe2O3 core–shell nanoparticle precursors. These core–shell nanoparticles weremade using a sequential synthetic approach. They could form FePt alloysand alloy-containing nanocomposites through a solid-state reaction at>400 °C. The chemical compositions of FePt alloys were controllable by usingPt@Fe2O3 core–shell nanoparticles that had the designed Pt core diameter and iron oxide shell thickness.We show that face-centred tetragonal (fct) FePt@Fe core–shell nanoparticles could be made fromPt@Fe2O3 core–shell nanoparticles with 5% hydrogen in argon(v/v). Furthermore, various FePt alloys and alloy-containing nanocomposites includingmetastable intermediate phases could be obtained. The materials were characterized byhigh resolution scanning transmission electron microscopy (HR-STEM), energy dispersivex-ray (EDX) spectroscopy, powder x-ray diffraction (PXRD), parallel electron energy lossspectroscopy (PEELS), and superconducting quantum interference device (SQUID)magnetometry. These materials could have potential applications as permanent hardmagnets and data storage media.