| Magnetic devices that exhibit the giant magnetoresistance effect (GMR) are used in computer disk drive and developing solid state memory applications. Demand for increased storage density and higher data rates continue to drive device size down, to deep submicrometer dimensions, while increasing operating speeds toward the GHz range. In order to maintain this trend, a detailed understanding of the high-speed dynamical response of submicrometer dimension magnetic structures is required.; We have developed a high bandwidth technique to measure the dynamical response of individual micrometer sized GMR devices. This has led to the first measurements of the ferromagnetic resonance frequency of individual micrometer sized magnetic elements. We have also made the first measurements of the real time magnetization reversal process, and the first demonstration of precession driven switching in individual micrometer sized devices.; We present the high frequency precessional response of GMR devices to 200 ps duration field pulses, 100 ps risetime field steps and 1–5 GHz oscillating fields. Resonance frequencies in the range of 2–5 GHz have been observed. Comparison of the time and frequency domain dynamical response to single domain and micromagnetic models yield a Landau-Lifshitz-Gilbert damping parameter close to α = 0.02.; Magnetization reversals, due to pulsed fields with duration as low as 230 ps have been observed. The thresholds for switching as a function of pulse duration and amplitude have been measured. The data indicate a variation of switching mechanism with field amplitude. Furthermore, single-shot observation of switching events show the possibility of driving the device into metastable states. The data is evidence of non-uniform magnetization configurations during switching as well as disorder that pins micromagnetic structure within the device. |
