Mossbauer Characterization of Iron Oxide Nanoclusters Grown within Aluminosilicate Matrices
Abstract
Mossbauer spectroscopy uses the resonant absorption of nuclear radiation by 57Fe to probe the electronic and internal magnetic structure of iron based magnetic materials. The technique has a characteristic measuring time of 10 ns enabling investigation of spin relaxation phenomena in nanoscale particles; and determination of their magnetic properties in the absence of externally applied magnetic fields. We report on Mossbauer studies of gamma-Fe2O3 nanoparticles synthesized within hexagonally packed mesoporous MCM-41 aluminosilicate matrices with cylindrical pores of 2.5 nm diameter. Data analysis allowed differentiation of particle-matrix interfacial versus particle-core interior iron sites. Interfacial iron atoms experience large electric field gradients resulting in quadrupole splitting values of change in E(q)(surface)=(1.25 plus/minus 0.05) mm/s, while core atoms exhibit smaller values of change in E(q)(core)=(0.73 plus/minus 0.05) mm/s at room temperature. Similarly, differences were observed in the values of the internal hyperfine fields at low temperatures indicating reduced strength in the exchange interactions at the particle surface, with interfacial atoms experiencing internal fields H(hf)(surface)=(458 plus/minus 1) kOe reduced relative to the core H(hf)(core)=(488 plus/minus 1) kOe at 4.2 K. Particle/matrix interactions at the surface appear to perturb the electronic interactions deeper into the core than the magnetic exchange interactions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2003
- Accession Number
- ADP014337
Entities
People
- A. B. Dominguez
- Georgia C. Papaefthymiou
- Rosa B. Scorzelli
Organizations
- Villanova University