Abstract
Cobalt ferrite nanoparticles of different stoichiometries synthesized by a sol–gel autocombustion method were used as a starting material to obtain high-moment Fe50Co50 and Fe66Co34 metal nanoparticles by topochemical hydrogen reduction. Structural and magnetic investigations confirmed the formation of FeCo nanoparticles with crystallite sizes of about 30 nm and magnetization at 0.5 T of ~265 Am2/kg (0 K), which was larger than the expected bulk value, likely because of the incorporation in the body-centered cubic (bcc) FeCo structure of the residual C atoms present on the surface of the oxide particles. Temperature-dependent magnetization measurements in the H2 atmosphere were also performed to investigate in detail the reduction mechanism and the effect of an external magnetic field on the process efficiency.
Highlights
Introduction published maps and institutional affilHigh-magnetic-moment nanoparticles (MNPs), such as metallic Fe, Co, α00 -Fe16 N2, and FeCo(Ni) binary alloys, have been the subject of intense research activity, owing to their potential applications in many different fields [1,2,3,4,5,6,7,8] exploiting their high saturation magnetization (MS ) which exceed by a factor of two or more the typical values of oxide materials (e.g., Fe3 O4 and CoFe2 O4 ) [5]
High-moment FeCo nanoparticles with tunable compositions can be obtained by topochemical H2 reduction (~350 ◦ C) of Co-ferrite nanoparticles with different Fe/Co ratios
FeCo alloy nanoparticles with an average crystallite size of ~30 nm featured by a high magnetization (~265 Am2 /kg at 0.5 T of ~265 Am2/kg (0 K) and 0.5 T), significantly larger than the values of the
Summary
High-magnetic-moment nanoparticles (MNPs), such as metallic Fe, Co, α00 -Fe16 N2 , and FeCo(Ni) binary alloys, have been the subject of intense research activity, owing to their potential applications in many different fields [1,2,3,4,5,6,7,8] exploiting their high saturation magnetization (MS ) which exceed by a factor of two or more the typical values of oxide materials (e.g., Fe3 O4 and CoFe2 O4 ) [5]. Different from oxide materials, metallic nanoparticles can be toxic, owing to their strong reactivity with oxygen, and they must be covered with a biocompatible shell, such as carbon [9,10,11], SiO2 [12], or Au [13]. In a non-oxidizing environment, the chemical activity of zero-valent metallic particles can be exploited to catalyze specific iations.
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