AVS 46th International Symposium
    Magnetic Interfaces and Nanostructures Technical Group Wednesday Sessions
       Session MI-WeA

Invited Paper MI-WeA7
High-Speed Dynamics of Submicrometer GMR Devices

Wednesday, October 27, 1999, 4:00 pm, Room 618/619

Session: Giant Magnetoresistance
Presenter: S.E. Russek, National Institute of Standards and Technology
Correspondent: Click to Email
Most of the applications of GMR and spin-dependent tunneling devices require them to be very small (line widths of ~300 nm) and very fast (operation frequencies > 1 GHz). The simplest devices typically consist of 4 to 10 layers of magnetic, nonmagnetic, insulator, and conducting materials with thicknesses of 0.6 nm to 10 nm. In this talk I will present high-speed measurements of sub-micrometer spin valves being driven by magnetic field impulses and step excitations with peak widths and ristimes of less than 300 ps. We have observed sub- 300 ps rotations and switching (180 degree rotation) of these devices and free induction decay (damped precessional motion) with characteristic frequencies of 2 - 6 GHz. The response of the devices have been compared to Landau-Lifshitz-Gilbert (LLG) micromagnetic simulations and high-speed measurements of magnetization rotation in sheet films using second-harmonic MOKE. The value of the dynamical parameters of the small devices, such as the damping constant, have been compared to those measured using more traditional methods on larger samples, with a smaller range of motion of the magnetization, and a less complex layer structure. The effect of disorder due to edge roughness, surface roughness, and variable interlayer coupling have been studied using LLG simulations and the results have been compared to the dynamical response of real devices to assess the importance of disorder in real systems. Both the damping constant and the degree of disorder are shown to be important in high-speed operation of these devices.