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Enhanced orbital magnetism in Fe(50)Pt(50) nanoparticles
C Antoniak1, J Lindner, M Spasova
1Experimentalphysik-AG Farle, Fachbereich Physik, Universität Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg, Germany.
Physical Review Letters
|October 10, 2006
Summary
This study investigated Fe(50)Pt(50) nanoparticles, revealing that removing organic ligands and oxide shells significantly enhances magnetic properties. Thermal treatment promotes the L1(0) phase, increasing coercivity and altering magnetic moments.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Monodisperse Fe(50)Pt(50) nanoparticles are crucial for magnetic applications.
- Surface contaminants like organic ligands and oxide shells can impede optimal performance.
- Understanding the effects of purification and annealing on magnetic properties is essential.
Purpose of the Study:
- To investigate the impact of removing surface contaminants on the magnetic properties of Fe(50)Pt(50) nanoparticles.
- To analyze the structural and magnetic changes induced by thermal treatment.
- To correlate crystallographic phase transitions with magnetic behavior.
Main Methods:
- Synthesis of monodisperse Fe(50)Pt(50) nanoparticles (6.3 nm mean diameter).
- Surface contaminant removal using soft hydrogen plasma.
- X-ray absorption and magnetic circular dichroism spectroscopy at Fe and Pt L(3,2) edges.
- Extended X-ray absorption fine structure (EXAFS) analysis.
- Thermal treatment and magnetic property measurements (coercive field).
Main Results:
- Complete removal of organic ligands and oxide shells resulted in a pure metallic state.
- Thermal treatment increased the coercive field by a factor of 6.
- Significant increase (330%) in orbital magnetic moment at Fe sites; decrease (30%) at Pt sites.
- Effective spin moments remained unchanged.
- EXAFS indicated crystallographic changes towards the L1(0) phase.
Conclusions:
- Surface purification and subsequent thermal treatment dramatically enhance the magnetic coercivity of Fe(50)Pt(50) nanoparticles.
- The observed changes in orbital magnetic moments are linked to the transition towards the ordered L1(0) phase.
- These findings provide insights into tailoring magnetic properties of alloy nanoparticles for advanced applications.
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