Date of Award

Spring 1-1-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Margaret M. Murnane

Second Advisor

Henry C. Kapteyn

Third Advisor

Daniel S. Dessau

Fourth Advisor

Ivan I. Smalyukh

Fifth Advisor

Thomas J. Silva

Abstract

Next-generation magnetic-memory devices and heat-assisted magnetic-recording applications will require a better understanding of magnetic multilayers and their interactions with optical-laser pulses. In this thesis, by combining the advantages of ultrabroad-band extreme-ultraviolet light including ultrafast time resolution, element selectivity and tabletop easy access, I report three findings in the study of ultrafast magnetization dynamics in itinerant ferromagnets. First, I experimentally prove that the transverse magneto-optical Kerr response with extreme-ultraviolet light has a purely magnetic origin and that our experimental technique is an artifact-free ultrafast magnetic probe. Second, I demonstrate the first ultrafast magnetization enhancement driven by ultrafast spin currents in Ni/Ru/Fe multilayers. Third, I engineer the sample system by choosing either insulating or spin-scattering spacer layers between the Ni and Fe magnetic layers and by structural ordering. Then, I control the competition between ultrafast spin-flip scattering and superdiffusive spin-current mechanisms; either of these processes may to be the dominant mechanism in ultrafast demagnetization.

Finally, I report two continuing experiments that are promising for future ultrafast magnetization studies with extreme-ultraviolet sources. These experiments are resonant-magnetic small-angle-scattering and the generation of bright circularly polarized high harmonics accompanied by a demonstration of the first x-ray magnetic circular dichroism with a tabletop system.

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