MICROSTRUCTURE OF FeCo–Cu NANOGRANULAR FILMS WITH GIANT MAGNETORESISTANCE

摘要

A series of (Fe50Co50)xCu1-x granular films were prepared using a magnetron-controlled sputtering system. The microstructure and giant magnetoresistance of FeCo–Cu films deposited at room temperature and then annealed at various temperatures were investigated through X-ray diffraction, transmission electron microscope and conventional four-probes method under room temperature, respectively. The results revealed that FeCo–Cu films consisted of fine FeCo granules uniformly dispersed in the Cu matrix and formed fcc structure. Meanwhile the Cu(111) interplaner lattice spacing decreased with increasing magnetic volume fraction (x) due to the presence of the metal coherent interface strains and FeCo–Cu alloying. Upon varying the magnetic volume fraction (x), the giant magnetoresistance of as-deposited FeCo–Cu films reached a maximum of about 0.7% at the volume fraction of 31%, corresponding to the fact that the giant magnetoresistance has a non-monotonic relationship with the granule size. In addition, the relationship between the full width at half maximum (FWHM) or the sensitivity of the giant magnetoresistance and the volume fraction are discussed in detail.