The giant magnetoresistance (GMR) effects in sandwiched Co/Cu/Co and Co/CuM
n/Co structures have been investigated. The GMR oscillates with the spacer
thickness for both cases, but nearly antiphased. With diluted Mn atoms in t
he Cu spacer, the GMR curve as a function of the magnetic field changes a l
ot, and the saturation/switching field for GMR can be reduced greatly compa
red with that in Co/Cu/Co systems. This may suggest one way to obtain a hig
hly sensitive GMR.