Influence of a surfactant on hyperfine magnetic interactions in goethite nanoparticles

Structural and magnetic characteristics of nanosized goethite (α-FeOOH) samples prepared by chemical precipitation of an iron (III) salt and alkali in aqueous solutions with different contents of a surfactant (ethyl alcohol) have been investigated. Changes in the morphology, structure, and sizes of antiferromagnetic nanoparticles, caused by the presence of the surfactant in the deposition solution, have been established by Mössbauer spectroscopy, magnetic measurements, X-ray diffraction, and electron microscopy. It is determined that an increase in the surfactant concentration leads to the bimodal size distribution of nanoparticles; in this case, the fraction of small (<10 nm) isolated particles in the sample increases and the degree of ordering of larger particles (50–100 nm) increases with a change in their shape from spherical to needle-like.