Extreme Ultraviolet Spectroscopy of Ultrafast Excitations in Magnetic Alloys

Magnetic materials play a vital role in modern technology, serving as essential components in a wide range of applications from power generation to data storage. However, there are still many open questions about the nature of the complex quantum mechanical phenomena and many-body interactions which shape the landscape of ferromagnetism. The next generation of logic devices may rely on fast switching of magnetic states. Electronic control of magnetic states is limited to nanosecond timescales. However, we have a faster tool. Pulsed lasers can measure and manipulate magnetic materials on their fundamental timescales. In this thesis, I present experiments in which I manipulate magnetic states in alloys on their fastest timescales: ranging from few-femtoseconds spin-transfers in Heusler alloys to magnetization reorientations in ferrimagnets which take tens of picoseconds. I utilize high harmonic generation (HHG) to produce an extreme ultraviolet probe for resonant measurements of the transverse magneto-optical Kerr effect (TMOKE) at the tabletop X-MATTER beamline. In Chapter 4, by tuning the driving laser, I measure across the entire M-edges of transition metals within Heusler alloys with unprecedented resolution in both probing energy and time. Furthermore, I present the first fluence-dependent measurements of spin-transfer. In Chapter 5, I present the first ultrafast study of the material TbMn6Sn6. I measure a laser-induced spin reorientation on its natural timescale. I present a time-dependent model of the laser-induced reorientation which arises from competing temperature-dependent magnetocrystalline anisotropies. In this thesis, I examine the intricate relationship between energy, angular momentum, bonding, and quantum mechanical exchange within the complex many-body physics of magnetism in condensed matter systems