AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI-WeM

Paper MI-WeM1
Direct Measurements of Spin Momentum Transfer Induced Dynamics

Wednesday, November 5, 2003, 8:20 am, Room 316

Session: Current-Induced Magnetic Switching and Excitations
Presenter: W.H. Rippard, National Institute of Standards and Technology
Authors: W.H. Rippard, National Institute of Standards and Technology
M.R. Pufall, National Institute of Standards and Technology
S. Kaka, National Institute of Standards and Technology
S.E. Russek, National Institute of Standards and Technology
T.J. Silva, National Institute of Standards and Technology
Correspondent: Click to Email
Slonczewski and Berger first predicted that the angular momentum from a spin-polarized current can be transferred to a ferromagnetic film creating a torque on the film magnetization, the so-called spin momentum transfer (SMT) effect. Previous work has shown that for sufficiently high current densities and applied magnetic fields, there occurs an abrupt increase in the dc resistance of point contact junctions or nanopillar devices. In accordance with theoretical predictions, these steps have been attributed to the onset of coherent magnetization dynamics. We will discuss our recent results from studying these excitations directly in a number of different materials, sample geometries, and applied field geometries. In general we find that the excitations can be well described with the Kittel equation for magnetization dynamics. We commonly observe these excitations from frequencies below 5 GHz to greater the 25 GHz. We have found that these linewidths are often as narrow as 20 MHz and persist for fields from H = 200 Oe to ~1 T, although the specifics depend on the particular geometry and material of the device under study. We also compare these results to single-domain model simulations of SMT induced dynamics and find good agreement between the simulated and measured behavior.