Nano-granular FePt-Ag composite film - Its magnetic and magnetotransport properties

FePt/Ag multiplayer films are fabricated by laser ablation deposition technique onto quartz substrate and ex-situ annealed in vacuum with annealing temperature in the range of 400 - 630 degreesC. Face centered tetragonal (fct) FePt nano grains are developed in annealed films. With changing in FePt layer thickness and annealing temperature, the FePt grain size can be controlled from below 10 nm to around 20 nm. Correspondingly, the film magnetic coercivity increases from 4.7 to 15 KOe. Giant magnetoresistance effect (GMR) is found in this composite film system. The GMR ratio is sensitive to the film microstructure and the variation is interpreted based on the spin dependent scattering of conduction electrons at the interface between FePt and Ag grains.