This thesis discusses the application of coherent, ultrafast beams of soft x-ray light from high-order harmonic generation (HHG) to study thermal, acoustic, and magnetic processes in nanostructures. This short-wavelength light is a uniquely powerful probe of surface dynamics since it has both a very short wavelength and duration.;First, this thesis reports the first observation and quantitative measurements of the transition from diffusive to ballistic thermal transport for the case of heat flow away from a heated nanostructure into a bulk substrate. This measurement provides insight into the fundamentals of thermal energy transport away from nanoscale hot spots, and demonstrates a fundamental limit to the energy dissipation capability of nanostructures. Further, we propose a straightforward correction to the Fourier law for heat diffusion, necessary for thermal management in nanoelectronics, nano-enabled energy systems, nanomanufacturing, and nanomedicine.;Second, this work discusses dynamic measurements of ultra-high frequency surface acoustic waves (SAW) and the first SAW dispersion measurement in a nanostructured system. These results are directly applicable to adhesion and thickness diagnostics of very thin films.;Finally, this thesis reports the first use of light from HHG to study magnetic orientation. Using the transverse magneto-optic Kerr effect and soft x-ray light near the M-absorption edges of Fe, Co, and Ni, magnetic asymmetries up to 8% are observed from thin Permalloy (Ni80Fe20) films. This signal is 1-2 orders of magnitude higher than that observed using optical methods, showing great promise for dynamic imaging of domain flipping at the 100 nm level.
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