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MA: Fachverband Magnetismus

MA 40: Poster II: Bio- and Molecular Magnetism (1-9); Magnetic Coupling Phenomena/Exchange Bias (10-15); Magnetic Particlicles and Clusters (16-29); Micro and Nanostructured Magnetic Materials (30-51); Multiferroics (52-64); Spin Injection in Heterostructures (65-67); Spin-Dyn./Spin-Torque (68-93); Spindependent Transport (94-108)

MA 40.73: Poster

Freitag, 27. März 2009, 11:00–14:00, P1A

Spin wave generation by photon coupled exchange magnons — •Vitaliy I. Vasyuchka, Christian Sandweg, Alexander A. Serga, and Burkard Hillebrands — FB Physik and Forschungszentrum OPTIMAS, TU Kaiserslautern, Germany

The behavior of a parametrically driven magnetic medium after the pumping source is switched off defines the important problem of pumping-free evolution of a non-equilibrium magnon gas.

A parallel electromagnetic pumping process creates pairs of photon coupled exchange magnons at half of the pumping frequency. These pairs induce a microwave magnetic field which is coherent with the pumping one but is shifted in phase. Thus the net pumping is effectively reduced in a stationary state. Switching the pumping source off is accompanied by an increase of the net magnetic field at the pumping frequency.

We report on the first observation of the energy transfer in the magnon gas caused by the influence of this field. The experiment was performed using a tangentially magnetized yttrium-iron-garnet (YIG) film. A microwave pumping pulse was supplied to the microstrip transducer. The signal irradiated by the YIG sample at half of the pumping frequency was picked up by the same microstrip. Just after the pumping pulse is switched off we detected a sharp peak at the end of this signal. The appearance of the peak is interpreted as a result of the parametric generation of long-wave spin waves by the non-compensated internal field, which acts as a pump.

Financial support by the DFG (SFB/TRR 49) is acknowledged.