Evidence for a short spin diffusion length in permalloy from the giant magnetoresistance of multilayered nanowires

We present magnetization and giant magnetoresistance (GMR) measurements per formed on two series of electrodeposited Py/Cu multilayered nanowires (Py = Ni80Fe20) of diameter null set =90 nm. The multilayers of the first series are composed of a conventional stacking of Py and Cu layers and the GMR is studied as a function of the Cu thickness for a constant Py thickness. The multilayers of the second series are composed of Py/Cu/Py trilayers unifor mly distributed along the filament and separated from each other by thick C u layers. For this second series, magnetic and GMR properties were investig ated as a function of the Py layer thickness and our magnetization measurem ents demonstrate that, for Py layers thinner than about 90 nm, the magnetic moments of the two Py layers of a trilayer are approximately antiparallel at zero field. Analysis of the GMR data using the Valet-Fert model allows u s to estimate that the spin diffusion length in Py, L-sf((PY)) , is between 3.3 and 5.3 nm. [S0163-1829(99)06125-1].