Does Giant Magnetoresistance Survive in Presence of Superconducting Contact?

.V .Lom The giantm agnetoresistance (G M R)offerrom agnetic bilayerswith a superconducting contact (F1/F2/S) is calculated in ballistic and di(cid:11)usive regim es. A s in spin-valve,itisassum ed thatthe m agnetization in the two ferrom agnetic layersF1 and F2 can be changed from parallelto antiparallel. It is shown that the G M R de(cid:12)ned asthechangeofconductancebetween thetwo m agnetic con(cid:12)gurationsisan oscillatory function ofthe thicknessofF2 layerand tendsto an asym ptotic positive value at large thickness. This is due to the form ation ofquantum wellstates in F2 induced by A ndreev re(cid:13)ection atthe F2/S interface and re(cid:13)ection atF1/F2 interface in antiparallelcon(cid:12)guration.In the di(cid:11)usive regim e,ifonly spin-dependent scattering ratesin the m agnetic layersare considered (no di(cid:11)erence in Ferm iwave-vectorsbetween spin up and down electrons)then theG M R issupressed dueto the m ixing ofspin up and down electron-hole channelsby A ndreev re(cid:13)ection.