Stabilization of surface spin glass behavior in core/shell-Fe67Co33/CoFe2O4 nanoparticles
Abstract
Magnetic properties of Co33Fe67--CoFe2O4 (core-shell) nanoparticles are presented. Both dc magnetization and ac susceptibility measurements indicate a spin glass (SG) like transition occurring at T F ~ 175 K. The SG nature of the transition is also confirmed by the field dependence of the freezing temperature T F(H) following the well known Almeida--Thouless line, δT F ~ H 2 / 3 . Additionally, the particles exhibit a large exchange bias (H EB ~ 1357 Oe) arising from the core-shell (ferromagnetic-SG) coupling. The unusually high SG transition temperature and large exchange bias effects are attributed to a combination of several factors including the thickness of the amorphous oxide shell and large values of the exchange and anisotropy constants associated with the CoFe2O4 shell.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2011
- Bibcode:
- 2011APS..MARQ19010J