Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light

<p>Next-generation magnetic-memory devices and heat-assisted magnetic-recording applications\&nbsp;<span style="line-height: 1.6em;">will require a better understanding of magnetic multilayers and their interactions with optical-laser\&nbsp;</span><span style="line-height: 1.6em;">pulses. In this thesis, by combining the advantages of ultrabroad-band extreme-ultraviolet light\&nbsp;</span><span style="line-height: 1.6em;">including ultrafast time resolution, element selectivity and tabletop easy access, I report three\&nbsp;</span><span style="line-height: 1.6em;">findings in the study of ultrafast magnetization dynamics in itinerant ferromagnets. First, I experimentally\&nbsp;</span><span style="line-height: 1.6em;">prove that the transverse magneto-optical Kerr response with extreme-ultraviolet light has\&nbsp;</span><span style="line-height: 1.6em;">a purely magnetic origin and that our experimental technique is an artifact-free ultrafast magnetic\&nbsp;</span><span style="line-height: 1.6em;">probe. Second, I demonstrate the first ultrafast magnetization enhancement driven by ultrafast\&nbsp;</span><span style="line-height: 1.6em;">spin currents in Ni/Ru/Fe multilayers. Third, I engineer the sample system by choosing either\&nbsp;</span><span style="line-height: 1.6em;">insulating or spin-scattering spacer layers between the Ni and Fe magnetic layers and by structural\&nbsp;</span><span style="line-height: 1.6em;">ordering. Then, I control the competition between ultrafast spin-flip scattering and superdiffusive\&nbsp;</span><span style="line-height: 1.6em;">spin-current mechanisms; either of these processes may to be the dominant mechanism in ultrafast\&nbsp;</span><span style="line-height: 1.6em;">demagnetization. Finally, I report two continuing experiments that are promising for future\&nbsp;</span><span style="line-height: 1.6em;">ultrafast magnetization studies with extreme-ultraviolet sources. These experiments are resonant magnetic\&nbsp;</span><span style="line-height: 1.6em;">small-angle-scattering and the generation of bright circularly polarized high harmonics\&nbsp;</span><span style="line-height: 1.6em;">accompanied by a demonstration of the first x-ray magnetic circular dichroism with a tabletop\&nbsp;</span><span style="line-height: 1.6em;">system.</span></p>
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University of Colorado Boulder
Boulder, CO
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