NEGATIVE SPIN-VALVE EFFECT IN CO65FE35 AG/(CO65FE35)(50)GD-50 TRILAYERS/

A minimum of the magnetoresistance under low fields has been observed with a Co65Fe35/Ag/(Co65Fe35)(50)Gd-50 trilayer at 4.2 and 300 K. This negative spin-valve effect is explained by the scattering of the cond uction electrons by the Co or Fe moments included in two different str uctures: a polycrystalline (Co65Fe35) and an amorphous one [(Co65Fe35) (50)Gd-50]. The Gd moments allow one to control the magnetic configura tion of the transition-metal moments of the layers but are inefficient for the magnetoresistance. This interpretation is confirmed by measur ements using high pulsed fields.