Exchange bias effect in Co nanoparticles embedded in Cr2O3 matrix

DINA TOBIA; ELIN WINKLER; ROBERTO ZYSLER; HORACIO TROIANI; DINO FIORANI

San Carlos de Bariloche

Conferencia; 13th International Conference on Solid Films and Surfaces; 2006

The nanostructures that present ferromagnetic/antiferromagnetic (FM/AFM) interfaces show hysteresis loop shift and enhance of the coercivity. These phenomena are attributed to the exchange interaction at the FM/AFM interface that induces an unidirectional anisotropy below the Néel temperature TN. The study of the exchange bias phenomena in nanoparticles has special interest because improve the performance of the permanent magnetic materials and increase the superparamagnetic limit for their use as magnetic recording media.  In this work we present the synthesis and study of the magnetic properties of 6 nm Co nanoparticles embedded in an AFM Cr2O3 matrix and Al2O3 non-magnetic matrix. When the Co nanoparticles are in the AFM matrix present a shift of the hysteresis loop when is measured after field cooling the sample through TN = 308 K. The maximum exchange field was observed for a field cooling of 2000 Oe. Moreover the exchange interaction enhances the magnetic anisotropy of the Co nanoparticles shifting the blocking temperature to room temperature.  We compare these results with the behaviour of the Co nanoparticles embedded in the Al2O3 matrix.