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From Solitons to Precessional Dynamics and Chaos - Nonlinear Spin Waves in Magnetic Thin Films

From Solitons to Precessional Dynamics and Chaos - Nonlinear Spin Waves in Magnetic Thin Films Carl E. Patton, Department of Physics, Colorado State University (DMR-0108797).

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From Solitons to Precessional Dynamics and Chaos - Nonlinear Spin Waves in Magnetic Thin Films

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  1. From Solitons to Precessional Dynamics and Chaos - Nonlinear Spin Waves in Magnetic Thin Films Carl E. Patton, Department of Physics, Colorado State University (DMR-0108797) The precessional dynamics of the magnetic moments and macroscopic magnetization in thin films represents an important component of fundamental nonlinear physics as well as more specific venues of ferromagnetic resonance, spin wave instability, and solitons. A basic understanding of the ways in which spin waves are generated and solitons are formed continues to be a key challenge. The structure: A yttrium iron garnet (YIG) film in a microstrip structure. Fundamental phenomena: Spin wave instability. Rise time generated spin waves. Ferromagnetic resonance. Relaxation processes. Soliton production by modulational instability. Applications: Radar. Digital signal processing. Secure communications

  2. The Colorado State University Magnetics Laboratory in the Department of Physics is engaged on research on linear and nonlinear precesisonal dynamics in yttrium iron garnet (YIG) magnetic thin films. Magnetic dipoles or the magnetization of a given material or thin film precess around an applied magnetic field in much the same way that a gyroscope precesses around the earth’s magnetic field. The transducer structure shown above can be used with input microwave signals (cw or pulsed) and dc pulses to generate linear and nonlinear spin waves. The are waves of these precessing spins that can propagate from input to output, as the diagram and photograph above. The output signal can be a microwave pulse, a soliton, or a train of solitons. Microwave magnetic envelope solitons are robust non-dispersive wave packets or pulses that have important fundamental properties such as constant phase profiles, multiple peaks in the case of higher order soliton modes, and intact crossover after collision.

  3. Pulse Generator Oscillo -scope Trig. Static field Wave vector k H0 Microstrip lines YIG film Substrate Recent results: rise time generated spin waves Input MAGNET POLE MAGNETIC FILM STRIP Output Time and space resolved Brillouin light scattering (BLS) avi file for the generated spin waves: leading edge pulse followed by trailing edge pulse. PROPAGAT I ON INPUT ANTENNA

  4. One recent result: Apply a “dc” (non-microwave) pulse (red trace in graph) to the microstrip line on the left. The rise time portion of the pulse (and the trailing edge as well) serves to generate spin waves. The spectrum of the spin waves is determined by the spatial and temporal harmonics of the drive signal and the spin wave dispersion relation for the yttrium iron garnet (YIG) magnetic film. These spin waves then propagate along the film strip to the output and may be detected on an oscilloscope or by Brillouin light scattering (BLS). The photograph shows the laser beam probe for the BLS detection. Time and space resolved BLS techniques have been used to “see” these spin wave pulses as they propagate in the film. The width of the YIG film is 2 mm and the propagation distance shown is 8 mm. One sees two spin wave pulses in sequence, one for the leading edge and one for the trailing edge.

  5. Personnel and Recent Accomplishments Carl E. Patton (PI) Invited lectures (most recent): "A romp through low and high power magnetic loss parameters and measurement techniques for microwave ferrites" "New materials and configurations for 10-100 GHz microwave devices, " IEEE International Microwave Symposium 2004, Fort Worth, Texas, June 7, 2004.. Spin wave dynamics in thin films: Resonance saturation butterfly curve response in permalloy films. Rise time generated spin waves by dc pulses. Precession dynamics in thin films: Ferromagnetic resonance (FMR) relaxation by pulse and microwave methods. Two magnon scattering relaxation analysis for thin films. Origin of low and high field effective linewidth in ferrites. Microwave magnetic envelope solitons: Bright and dark soliton train generation Through spontaneous and induced modulational instability processes. Igor Kalinchenko Guest Scientist Pavol Krivosik Postdoctoral Fellow Mingzhong Wu Postdoctoral Fellow Sangita Kalarickal Ph .D. Candidate Kevin Smith Ph. D. Candidate Heidi Olson Ph. D. Candidate

  6. Igor Kalinchenko has been with the group for about one year. He has developed the time and space resolved imaging of rise time generated spin waves. Mingzhong Wu has been with the group for two years. He has performed measurements of higher order soltions (in press with Phys. Rev. B), and done the microwave measurements and analyses for soliton trains from self-modulational instaiblity (submitted to Phys. Rev. Letters) and done the rise time generated spin wave experiments. Pavol Krivosik has been with the group for two years. He has performed the theoretical analysis of high power spin dynamics in thin films and two and three magnon scattering relaxation. Six submissions from the group have been accepted for presentation at the upcoming Magnetism and Magnetic Materials Conference in Jacksonville, Florida in November 2004.

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