Perpendicular-current exchange-biased spin-valve evidence for a short spin-diffusion lenght in permalloy

We present the first measurements of giant magnetoresistance with current perpendicular to the layer planes (CPP-MR) of an exchange-biased spin-valve (EBSV) - a controllable spin-switch. Interpreted with the theory of Valet and Fert, data on EBSVs of permalloy (Py) with Cu yield an unexpectedly short spin-diffusion length in Py − l sf Py =5.5± nm. Such a short length has implications for the interpretation of Johnson's data on a Py/Au/Py spin-switch.