Evidence of giant magnetoresistance effect in heterogeneous nanogranular films produced by ultrashort pulsed laser deposition

Giant magnetoresistance effect is found in films of magnetic nanoparticles uniformly mixed with non-magnetic metallic nanoparticles produced by ultrashort pulsed laser deposition (uPLD). The uPLD, which uses femtosecond laser pulses, has been recently reported as a powerful technique for obtaining nanoparticles and nanogranular films. As-deposited Co-Cu and Fe-Ag films in a moderate volume fraction range of magnetic component (15-25\%) present detectable values of this magnetoresistive effect, although the average size of the particles is higher than in typical nanogranular materials for magnetoresistive applications. The determined longitudinal, transverse and perpendicular magnetoresistance behaviours, at the temperatures of 10 and 250K, confirm the strong influence of the production technique on the complex microstructure of these films and consequently on their peculiar magneto-transport properties. In perspective, by optimizing the production parameters, these nanogranular films appear very promising for potential application in magnetic recording and data storage technology.