Ultraschnelle Magnetisierungsprozesse in Mikro- und Nanomagneten

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The dynamic response of micro- und sub-micrometer-size spinvalve film elements on very fast magnetic field pulses will be studied on a time scale of 20 ps to 100 ns. Field pulses will be created by current pulses through micro strip-lines and alternatively by pumping a Schottky diode with femtosecond laser pulses. Magnetization precession and switching will be observed by measuring the giant magnetoresistance with a fast digital sampling oscilloscope. Mainly samples will be studied containing an epitaxial ferromagnetic Fe1-xCox free layer of high structural perfection grown by molecular beam epitaxy; magnetic anisotropies of these films are controlled in a wide range by variation of thickness and composition thus allowing experiments with well-known values of the parameters entering micromagnetic simulations. The influence of anisotropies, of temperature in relation to the Curie temperature and of exchange coupling to a second ferromagnetic layer will be investigated. In a joint experiment with a second research group the GMR signal will be captured simultaneously with a time-resolved scanning Kerr microscopy image to combine the advantages of these complementary methods.