Role of Structural Defects of Cobalt Ferrite as Target on Magnetic Properties of FM/fm Systems Prepared by PLD Technique

BILOVOL V,PAMPILLO L, SACCONE F

San Carlos

Conferencia; 5th Latin American Conference on metastable and Nanostructured Materials; 2012

A series of bilayers of ferromagnet (FM)/ferrimagnet(fm) type was grown on Si (111) substrate with Fe as FM and CoFe2O4 as fm, by means of the Pulsed Laser Deposition technique (PLD). In order to investigate the role of transferring the ?structural quality? of fm targets (CoFe2O4) on magnetic properties of the samples, we characterized magnetic properties of the latter, in particular, exchange bias (EB) effect. The model proposed by Nowak et al [1], successfully applied by them to a bilayer of the type FM/AFM (antiferromagnetic), holds that EB field depends on defects presented in the volume part of the AFM. Three different targets of cobalt ferrite were used for growing thin bilayer films. The targets were prepared on the base of chemically synthesized nanoparticles where different structural disorder was induced by means of distinct thermal treatments. The XRD technique shows clearly (1 1 1)-preferred orientation of CoFe2O4 layer. We observed that the sample prepared using CoFe2O4 nanoparticles synthesized at lowest temperature (and having in such a way the most important structural defects) revealed the smallest value of coercive field at room temperature when measuring M vs H curve. On the other hand, the sample prepared using the cobalt ferrite nanoparticles with the least amount of defects showed the highest value of coercive field. When the loops were acquired at 20 K after field cooled at H= 3T, the EB field was the highest for the sample with more structural disorder of cobalt ferrite as target during PLD procedure. In such a way, we established that the model of Nowak is valid too for a system with ferrimagnetic (CoFe2O4) layer instead of AFM one.