Magnetic Properties of Single-Domain Iron and Iron-Cobalt Particles Prepared by Borohydride Reduction

Abstract

Air-stable, single-domain Fe and Fe-Co particles prepared by the reaction of the metal salts with aqueous borohydride have higher coercivities and axial ratios if prepared in a magnetic field. Oxide and boride impurities are indicated by elemental analyses and lowered saturation magnetizations. Studies of coercivitiesand magnetizations as a function of temperature, remanence ratios, and rotational hysteresis measurements indicate single-domain behavior with coercivity controlled by shape and somewhat by crystalline anisotropy in approximate agreement with the predictions of the Jacobs-Bean “chain of spheres” model.

Physical properties of elongated inorganic nanoparticles

“…Oppegard et al already studied in 1961 the shape anisotropy of axially aligned Fe and FeCo nanoparticles prepared by the reduction in solution of Fe(II) salts under the effect of a magnetic field [425]. However, in this case, the shape anisotropy contribution to coercivity was strongly hindered by agglomeration phenomena.…”

Exchange Bias in Chemically Reduced FeCo Alloy Nanostructures

“…EB studies involving highly magnetic nanoparticles were performed in oxidized metallic Fe nanoparticles that were found to exhibit H E with an average particle size below 15 nm . Indeed, couple of the experiments performed with chemically synthesized FeCo resulted in products with high magnetic anisotropy such as Co or highly crystalline CoFe 2 O 4 making the origin of loop shift unclear. In addition, high coercivity in the range of 1.2–2.2 kOe at room temperature (RT) itself is intricate due to the contributions, such as shape anisotropy, magnetocrystalline anisotropy, size effect, or interfacial effects.…”

Magnetic inductor based on nanosize amorphous metal powder

“…Earlier work by Kim and Brock [5] on Fe-Co-B powders indicated that chains did not form in larger particles that were multi-domain in nature. In addition, experimental results presented by Oppegard et al [11] on iron and iron-cobalt powders produced by the borohydride reduction of iron sulfate/cobalt chloride solutions indicated that the powders exhibited single domain behavior. Their typical iron particles had a coercivity of 645 Oe.…”