Strain Anisotropies in Core/Shell Magnetic Nanostructures
Abstract
The magnetic properties of nanosized iron-oxo molecular clusters have been investigated via Moessbauer spectroscopy and compared to those of silica coated iron-oxide nanoparticles. The clusters, prepared by controlled hydrolytic iron polymerization reactions, contain a approx.= 1.2 nm diameter magnetic core of spin-coupled iron ions surrounded by a shell of benzoate ligands. The nanoparticles, prepared via sol-gel synthesis, contain a approx.= 4.0 nm average diameter gamma-Fe2O3 core coated by a shell of SiO2. Both systems exhibit magnetic bistability at low temperatures with estimated magnetic anisotropy constants of K(sub eff)=O.63x10 to the 5th J/cu cm for the clusters and K(sub eff) = 0.55 x103 J/cu cm for the particles. The similar values of K(sub eff) indicate that these two systems experience similar degrees of strain at the core/shell interface. This is further supported by the values of the quadrupole splitting, Delta E(sub Q)=O.77 mm/s for the clusters and Delta E(sub Q)=0.75 mm/s for the particles, pointing to same degree of distortion from pure octahedral or tetrahedral symmetry at the iron coordination sites for either system. Implications of these observations for the surface atomic structure of gamma-Fe2O3 nanoparticles are discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2001
- Accession Number
- ADP011014
Entities
People
- Georgia C. Papaefthymiou
Organizations
- Villanova University