Hamburg 2001 – scientific programme

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AM: Magnetismus

AM 17: Mikromagnetismus II (Dots, Partikel)

AM 17.2: Talk

Friday, March 30, 2001, 10:30–10:45, S 5.4

Hot spin injection: the precession of the magnetization — •S. Riesen, W. Weber, and H.C. Siegmann — Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich, Schweiz

Electrons injected into ferromagnets experience exchange coupling to the magnetization and spin-dependent scattering leading to excitations of the magnetization. By injecting currents of high density, these excitations have been observed in recent experiments. However, in these experiments the injection of electrons from a ferromagnet through nanocontacts occurs on time scales long compared to the relaxation of the magnetization into the direction of the effective field. This means that precession and relaxation of the magnetization are intertwined, making it impossible to uniquely interpret the existing experiments in terms of specific elementary processes.

We present a new experiment in which these disadvantages are avoided and in which the precession of the magnetization by hot spin injection can be measured. It turns out that precession frequencies equivalent to the application of a magnetic field of about 1 T may be generated at reasonable injected current densities in Fe, Co, and Ni, suggesting that the spin injection technique may be applied to technically relevant materials for precessional magnetization reversal. The precession mode of reversal is a highly attractive concept advancing the speed of magnetic data recording into the picosecond time scale.