Ultrafine FeCo Nanoparticles Isolated by Ultrathin Dielectric Shells for Microwave Application

Abstract

Low-dimensional soft magnetic materials are technologically important for miniaturization of magnetic devices. It is, however, challenging to maintain ferromagnetic response in nanosized magnetic material. In this work, ultrafine FeCo nanoparticles have been prepared by reactive pulsed laser deposition, which can be exchange coupled through ultrathin dielectric shells, even though their diameters are far below the superparamagnetic blocking limit. This unique core/shell structure guarantees ferromagnetic coupling and insulation of neighboring magnetic nanoparticles simultaneously. The nanoparticle film exhibits large saturation magnetization of 1.13 T, high electrical resistivity of 4200 μΩ·cm, maximum permeability of 120, a cutoff frequency of 1.7 GHz, and it is a promising material for microwave application.