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MA: Magnetismus

MA 18: Spin-Dynamics, Magnetization Reversal I

MA 18.2: Vortrag

Dienstag, 28. März 2006, 10:30–10:45, HSZ 403

Microwave assisted switching in Ni₈₁Fe₁₉ — •P. Martin Pimentel, H.T. Nembach, S. Hermsdörfer, and B. Hillebrands — Fachbereich Physik and Forschungsschwerpunkt MINAS, TU Kaiserslautern, Erwin-Schrödinger-Str. 56, 67663 Kaiserslautern, Germany

We present the study of the quasi-static switching behavior of a Ni₈₁Fe₁₉ ellipsoid under the influence of a microwave field by longitudinal magneto-optic Kerr effect magnetometry. The long axis of the ellipsoid is parallel to the quasi-static field in the plane of the element. The dimensions of the element are 160 µm x 80 µm x 10 nm. The switching behavior of the element is studied by measuring hysteresis curves with an applied microwave field perpendicular to the quasi-static magnetic field. The frequency of the microwave field was varied in the range of 500 MHz to 2.0 GHz in steps of 100 MHz and the microwave power is increased from -5 dBm to 35 dBm for each frequency. A strong reduction of the coercive field is observed for the microwave frequencies between 650 MHz to 900 MHz for the maximum output power of 35 dBm. This reduction can be described by two different mechanisms. The most important one is the enhancement of domain nucleation by the microwave field. The second, weaker mechanism is an enhanced growth of the reversed domain. This is due to the fundamental principle that every physical system favors the state with the lowest Gibbs free energy. We demonstrate that the switching process of elements, which is dominated by domain nucleation and propagation, can be stimulated by applying a transversal microwave field. This work is supported by the EU-RTN ULTRASWITCH (HPRN-CT-2002-00318).