Hamburg 2001 – wissenschaftliches Programm

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AM: Magnetismus

AM 3: Magnetowiderstand I

AM 3.1: Hauptvortrag

Montag, 26. März 2001, 14:00–14:45, S 5.2

Magnetization reversal by spin injection — •Albert Fert — Unité Mixte de Physique CNRS-Thomson and Université Paris-Sud, Orsay, France

The magnetization of a magnetic layer can be reversed by spin transfer from a spin polarized current (that is without applying a magnetic field), as predicted by Slonczewski in 1995 and confirmed by recent experiments. We will present measurements on sub-micronic Co/Cu/Co pillars in which a current is passed perpendicularly to the layers. The magnetic configuration, with parallel (P) or antiparallel (AP) moments of the Co layers, can be detected by GMR. We find that a positive current (electrons going from the thick Co layer to the thin one) can switch the configuration from AP to P, while switching from P to AP is induced by a negative current. This asymmetry is the signature of reversal by spin injection. The required current density is about 10⁷ A/cm². We will present the interpretation of our results in the model of Slonczewski and in a new model based on spin accumulation that we developed with P. M. Levy. At the present stage, it is not possible to really decide between these two types of models. Nevertheless, in both approaches, it turns out that, by optimizing the parameters of our samples, the critical currents can certainly be reduced. This will be of interest for application to the switching of sub-micronic magnetic devices.