Abstract
The magnetic properties of mixtures of ferrimagnetic (maghemite) and antiferromagnetic or nanoparticles have been studied by use of Mössbauer spectroscopy, neutron powder diffraction and magnetization measurements. The studies showed that the interaction with antiferromagnetic particles has a significant influence on the magnetic properties of the nanoparticles. It was found that mixing the nanoparticles with nanoparticles resulted in a faster superparamagnetic relaxation and a reduced coercivity compared to a sample consisting solely of nanoparticles. On the contrary, mixing of nanoparticles with nanoparticles resulted in a suppression of the relaxation and an increase in coercivity. These results suggest that the properties of the ferrimagnetic nanoparticles are influenced by the anisotropy of their neighboring antiferromagnetic particles. The dominating type of magnetic interaction between the particles in the composites seems to be exchange interaction between surface atoms of neighboring particles.
- Received 8 March 2004
DOI:https://doi.org/10.1103/PhysRevB.70.134416
©2004 American Physical Society