Superferromagnetism in chain-like Fe@SiO2 nanoparticle ensembles

• Published in: Journal of applied physics 2014-07, Vol.116 (3)
• Main Authors: Zeleňáková, A., Zeleňák, V., Mat'ko, I., Strečková, M., Hrubovčák, P., Kováč, J.
• Format: Article
• Language: English
• Subjects: Absorption spectra; Applied physics; Coercivity; Cooling; Core making; Dipole interactions; Iron; Magnetic dipoles; Magnetic moments; Magnetism; Nanocomposites; Nanoparticles; Oxidation; Process management; Self-assembly; Silicon dioxide; Temperature dependence; X ray spectra
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4890354

One-dimensional (1D) chain-like nanocomposites, created by ensembles of nanoparticles of with diameter ∼ 13 nm, which are composed of an iron core (∼4 nm) and a silica protective layer, were prepared by a self-assembly process. Chain-like Fe@SiO2 ensembles were formed due to strong magnetic dipole–dipole interactions between individual Fe nanoparticles and the subsequent fixation of the Fe particles by the SiO2 layers. X-ray near edge absorption spectra measurements at the Fe K absorption edge confirm that the presence of a silica layer prevents the oxidation of the magnetic Fe core. Strong magnetic interactions between Fe cores lead to long-range ordering of magnetic moments, and the nanoparticle ensembles exhibit superferromagnetic characteristics demonstrated by a broad blocking Zero-field cooling (ZFC)/field-cooling distribution, nearly constant temperature dependence of ZFC magnetization, and non-zero coercivity at room temperature. Low room-temperature coercivity and the presence of electrically insulating SiO2 shells surrounding the Fe core make the studied samples suitable candidates for microelectronic applications.