Surface anisotropy and exchange interaction of Co nanoparticles embedded in a Cr2O3 matrix

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

Buenos Aires, Argentina

Conferencia; At the Frontiers of Condensed Matter III; 2006

We study the effect of the exchange interaction at the interface of Co nanoparticles embedded in an antiferromagnetic Cr2O3 matrix. The samples were prepared by two methods: from chemical precipitation and from solid state reaction follow by calcination in an Ar2/H2 atmosphere. From the first method the samples consist in ~6 nm Co nanoparticles embedded in ~200 nm Cr2O3 matrix. From the second method the obtained ~6 nm Co nanoparticles are embedded in ~80 nm Cr2O3 nanoparticles. Both systems present exchange bias effect when are cooling applying a magnetic field through the matrix antiferromagnetic transition temperature TN=308 K. We found that the exchange field depends on the cooling field and the temperature. The maximum exchange field was observed cooling the sample with an applied field of 2000 Oe. We compare these results with the magnetic behavior of Co nanoparticles dispersed in a diamagnetic Al2O3 matrix.