Abstract:
Structural, microstructural, morphology and magnetoresistive properties of FexCuyAgz granular thin films exhibiting giant magnetoresistance were investigated. Several series of samples with wide concentration range were prepared by DC magnetron sputtering. The binary FeCu and FeAg systems are the end components of the ternary FexCuyAgz system. The compositions of the samples were determined by energy-dispersive X-ray analysis. X-ray diffraction patterns showed Ag(111) and Cu(111) peaks and the Fe peaks were not observed. The d-spacings calculated from the Ag(111) and Cu(111) peaks are smaller and greater than the standard bulk value for Ag and Cu, respectively, indicating a partial intermixing of Fe, Cu and Ag atoms. The electron diffraction patterns obtained on selected samples showed many Cu and Ag reflections and they also did not show any reflection from Fe. The electron micrographs show the granular structure of these films with typical granule size of 4-5 nm. The surface image of the FeAg films observed using a scanning electron microscope showed the presence of droplet-like Ag particles on the film surface. On the other hand the FexCuy and FexCuyAgz films are smooth without any Ag particles on the film surface. Surface morphology of some samples studied by atomic force microscopy showed that the films are smooth and their typical surface roughness is 0.5-2.0 nm. Magnetoresistance measurements on the samples up to 20 kOe showed typical superparamagnetic behaviour. We have obtained a maximum giant magnetoresistance ratio of 3.8% in these films measured at 300 K for an in-plane magnetic field of 20 kOe indicating an increase in the value of magnetoresistance due to Ag substitution in the FeCu films. Percolation limit for the Fe grains has also been obtained from the magnetoresistance data. (C) 2013 Elsevier B.V. All rights reserved.