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9.3.2006, 15:30
Jungiusstr. 9, Hörsaal III

SFB 668 - Seminar

Dr. Jun-Ichiro Ohe (ITP, Uni Hamburg):

A current induced spin fluctuation state in a mesoscopic magnetic wire

During the past decade, considerable progresses have been made in understan-ding the current-induced spin torque effect in magnetic nanowires. The spin torque effect can be observed not only in ferromagnetic metals but also in mag-netic semiconductors at low temperatures because of the low Curie tempera-ture. Semiconductors at low temperatures are well-known paradigms of mesos-copic quantum systems in which interference of electrons can be of consider-able importance. In such mesoscopic systems, the understanding of the phenomena related to the spin momentum transfer between the conduction electrons and the magnetization of the local spins is still in its infancy.

In this report, we investigate the current-induced magnetization switching effect in mesoscopic regions. We show that the current of mesoscopic nano-wires can generate spatio-temporal magnetization patterns in the magnetic domain. This is induced by the mesoscopic spin torque which creates effective random ferro-magnetic and anti-ferromagnetic couplings between the local spins. Above some critical diameter of the wire, a crossover from an ordered ferromagnetic to a time dependent spin fluctuation state occurs when the average current exceeds a critical value. We provide numerical evidence that the magnetic non-equilibrium state is signaled by conductance fluctuations at sufficiently low temperatures.

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