L 1 ordering and magnetic interactions in FePt nanoparticles embedded in MgO and SiO2 shell matrices

Abstract

FePt nanoparticles have been encapsulated in insulating and protective MgO shells, using a two step chemical process, in order to prevent sintering during the heat-treatment process required for the L1 0 ordering. The FePt nanoparticles were initially prepared using a standard polyol process and then dispersed in a magnesium oxide solution. As a basis for comparison FePt/ SiO 2 nanocomposites have been also synthesized using a modified aqueous sol-gel route as the second step. The magnetic and microstructural properties of FePt/ MgO and FePt/ SiO 2 nanocomposites are compared with those of FePt nanoparticles. The presence of oxide matrices leads to more homogeneous microstructures and better magnetic properties. While higher coercivity values have been obtained in FePt/ SiO 2 , the MgO matrix is proven to provide better physical and magnetic isolations of the FePt nanoparticles. However, for FePt:MgO molar ratios exceeding 1:20 no L1 0 ordering has been achieved.

Tailoring interlayer exchange coupling of ferromagnetic films across MgO with Fe nanoclusters

“…5(A), we again see the Wshape trend in J 1 with respect to NC position, but there is a strong asymmetry in the AF coupling strength.Examining the line cut at MgO thickness of 0.72 nm (red triangles) and starting from the negative end point where the NC are at the MgO/Co interface, we find J 1 = -0.03 erg/cm 2 . As the NC move vertically toward the zero NC position, we find a maximum AF coupling of J 1 = -0.10 erg/cm2 at a Fe NC position of -0.20 nm. As the NC continue to move, the coupling reaches a minimum AF coupling of J 1 = -0.07 erg/cm 2 at a Fe NC position of -0.08 nm.…”

Synthesis and characterization of carbon nanotubes decorated with Pt and PtRu nanoparticles and assessment of their electrocatalytic performance

“…Monodispersed Pt capped NPs were prepared by the polyol synthetic procedure [60]. In detail, diphenylether (20 mL), 1, 2Àdodecanediol (10 mmol) and oleylamine (5 mmol) were mixed in a spherical flask (50 mL) and refluxed under continuous stirring at 140 C for 10 min.…”

Low pressure bottom-up synthesis of metal@oxide and oxide nanoparticles: control of structure and functional properties

“…The film growth conditions have been chosen in order to have the same surface to volume ratio as the 9nm NP sample. By XPS analysis during oxidation and reduction cycle, we observed a stronger reducibility for NP, possibly because of the fact that exposed surface is (100) which is more favorable to oxygen release, instead of the (111) surface like in the case of the film.…”