Synthesis and Magnetic Properties of Co $_{1- {x}}$Ir$_{x}$ Alloy Nanoparticles for High-Frequency Applications

Co
_1-x
Ir
_x
(x=10,20,and 30) alloy nanoparticles were prepared using a high-temperature chemical reduction technique in an inert atmosphere for the first time. High-resolution electron microscopy studies show the formation of nearly monodispersed Co
_1-x
Ir
_x
alloy nanoparticles having the hexagonal close packed structure. The sizes of the particles were dictated by controlling the reaction parameters and the type of surfactants. Superconducting quantum interference device (SQUID) magnetometry studies showed soft magnetic behavior at 300 K and also at 5 K. The as-prepared, nearly dispersed nanoparticles were assembled and fixed on a polymer substrate. The microwave properties measured by ferromagnetic resonance at 9.61 GHz indicate a minimum line width of about 300 Oe