Magnetic properties of colloidal cobalt nanoclusters
- Autori: Torchio, R; Meneghini, C; Mobilio, S; Capellini, G; Garcıa, A; Prieto, J; Alonso, ML; Fdez Gubieda; Turco Liveri, V; Liveri, A; Longo, A; Ruggirello, AM; T, Neisius
- Anno di pubblicazione: 2010
- Tipologia: Articolo in rivista (Articolo in rivista)
- Parole Chiave: cobalt nanoparticles
- OA Link: http://hdl.handle.net/10447/50909
Abstract
Abstract. Co nanoclusters were synthesized by an inverse-micelle chemical route. The magnetic and microstructural properties of the nanoparticles have been analyzed as a function of the surfactant (AOT and DEHP) and the drying method. Microstructural analysis has been performed by TEM and XANES; magnetic properties have been studied by hysteresis loops and zero-field cooling - field cooling (ZFC-FC) curves. TEM images show 2 to 4 nm sized particles spherical in shape. XANES measurements point out a significant presence of Co3O4 with metallic Co and some Co2+ bound to the surfactant. The presence of antiferromagnetic Co3O4 explains the magnetic transition observed at low T in both ZFC-FC measurements and hysteresis loops. Finally, the presence of magnetic interactions explains the bigger effective cluster size obtained from hysteresis loops fits (6-10 nm) compared to the sizes observed by TEM (2-4 nm).