High frequency giant magnetoresistance in evaporated Co/Cu multilayers deposited on Si(111) and Si(100)

We report giant magnetoresistance (GMR) in Co/Cu multilayers deposited usin g high vacuum electron beam evaporation on Si(111) and Si(100). Samples gro wn on Si(111) show enhanced magnetoresistance and coercivity, which may be attributed to ill-defined interfacial boundaries between successive layers. Previous work exploring the frequency dependency of GMR has been done usin g microwave techniques to indirectly determine GMR. Our magnetoresistance d ata was obtained by replacing one side of a square loop antenna with a Co/C u multilayer and measuring the impedance. No effect on the magnitude of the GMR, due to high frequency test signals, was observed for a frequency rang e from dc to 5.5 GHz. (C) 1999 American Institute of Physics. [S0021-8979(9 9)05601-7].