Characterization and giant magnetoresistance effect in cobalt–silver granular films formed by MEVVA implantation

Abstract

Cobalt–silver granular thin films exhibiting giant magnetoresistance (GMR) effect were formed by Co implantation into Ag using a metal vapor vacuum arc (MEVVA) ion source. The magnetic field dependence and the temperature variation of the GMR effect and their relation with the processing conditions were studied and discussed in conjunction with results of Rutherford backscattering spectrometry, atomic force microscopy and magnetic force microscopy (MFM). For the best sample obtained in this study, the magnitude of the GMR effect measured at a magnetic field strength of 7.6 kOe increases from about 1% at room temperature to over 7% at 20 K. The coercive field H C in the perpendicular-to-film direction determined from GMR measurements showed an anomalous temperature variation that shows a maximum value at around 240 K and decreases with decreasing temperature from 240 to 20 K. The domain structures of the implanted granular films revealed by MFM images exhibit a very different feature compared with those of sputter deposited Co–Ag granular films.