Two-Phase Co–Cu Thin Films with Size Distribution of Ferromagnetic Nanostructures Optimum for Giant Magneto Resistance

Abstract

New thin-film microstructure, with a homogeneous distribution of a crystalized one phase Co-rich magnetic nanoparticles, embedded in a Cu-rich continuous paramagnetic matrix was obtained. This structure has many of the characteristics deemed optimal for Giant Magneto Resistance (GMR). These characteristics are; mean free path of the electrons in the matrix, granules/matrix interface roughness, the ferromagnetic concentration of the magnetic granules, and most importantly, the size distribution of the granules. This microstructure was created in Co-93at%Cu thin film, through spinodal decomposition after a short time of aging that reached equilibrium by a growth and coarsening process. Main goal of the present work was the enhancement of the microstructure in order to pinpoint the optimum microstructural and magnetic feature that improves the GMR sensitivity and stability in granular materials. Accordingly, Structural evolution of the thin films was controlled by the annealing time and temperature. Four-probe-technique was utilized to measure the GMR properties. GMR curve for a sample annealed at 150 °C was found to be stable and saturated even at low magnetic field (<5 kOe). Microstructural evolution and compositional analysis of the thin film was investigated using in-situ transmission electron microscopy (TEM) and the energy dispersive X-ray spectrometer (EDXS).