Ag-Fe3O4 Dimer Colloidal Nanoparticles: Synthesis and Enhancement of Magnetic Properties

This paper describes a solution-phase route to prepare Ag-Fe3O4 colloidal dimer nanoparticles (NPs) with a dumbbell-like shape. Results show enhancement of the magnetic anisotropy and large coercivity that are explained through the nonzero orbital moment, m(orb), and the related strong spin orbit interaction that can be induced by a lattice distortion of the Fe-O bond lengths. In particular, distortions of the octahedral sites in magnetite result in Fe 3d-O 2p mixing and O 2p to Fe 3d charge transfer which, together with crystal field effects, lifts the electronic degeneracy, leading to a nonzero m(orb). dc magnetization and ferromagnetic resonance were employed for analyzing the magnetic response of the reference Fe3O4 NPs and Ag-Fe3O4 dimer NPs samples, showing a very good agreement with the structural characterization.