AVS 53rd International Symposium
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI-TuA

Invited Paper MI-TuA3
Element-Resolved Phase and Amplitude of Magnetization Dynamics in Thin Magnetic Films

Tuesday, November 14, 2006, 2:40 pm, Room 2006

Session: Magnetic Thin Films and Multilayers
Presenter: D.A. Arena, Brookhaven National Laboratory
Authors: D.A. Arena, Brookhaven National Laboratory
E. Vescovo, Brookhaven National Laboratory
C.C. Kao, Brookhaven National Laboratory
Y. Guan, Columbia University
L. Cheng, Columbia University
W.E. Bailey, Columbia University
Correspondent: Click to Email
In high-speed (GHz range) magneto-electronics, both the phase and amplitude of precession of different constituents (e.g. layers, impurities) determines the dynamic response of the device. To date, most information on the relative phase and amplitude of precession of different elements in ferromagnetic (FM) films must be deduced from theoretical models developed to analyze dynamic measurements which average over the sample. We present the first measurements of element- and time-resolved ferromagnetic resonance (ETR-FMR) in magnetic thin films at GHz frequencies. With ETR-FMR the dynamic response of individual layers in complex structures can be measured as well as the precession of individual elements in an alloy or compound. ETR-FMR also provides extremely accurate measurements of the precession cone angle (to 0.2°) and the phase of oscillation (to 2°). With this degree of precision and the ability to detect the dynamics of individual elements, fundamental assumptions implicit in phenomenological theories such as the Landau-Lifschitz-Gilbert approach can be investigated in a direct fashion. We have used ETR-FMR to measure the response of specific elements and separate layers in several alloys and structures. These include the Fe and Ni moments in a single film of Ni@sub 81@Fe@sub 19@, layer-resolved FMR measurements of a pseudo-spin valve structure of two FM layers separated by a non-magnetic spacer (Ni@sub 81@Fe@sub 19@ / Cu / Co@sub 93@Zr@sub 7@), magnetic bilayers with dissimilar resonant frequencies, and magnetic alloys with engineered precession damping. In the pseudo-spin valve structure, ETR-FMR reveals weak coupling between the Ni@sub 81@Fe@sub 19@ and Co@sub 93@Zr@sub 7@ layers; such coupling is difficult to resolve in conventional FMR measurements. The unique capabilities of ETR-FMR in measuring precessional phase lags between different elemental moments will be discussed in relation to magnetic bilayers and engineered magnetic alloys.