Confinement-driven renormalization of magnon and phonon spectra in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Fe</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <

The authors reveal here how finite-size confinement reshapes spin and lattice excitations in Fe${}_{3}$O${}_{4}$ nanoparticles using time-of-flight neutron spectroscopy and numerical simulations. Confinement induces surface strain that softens and broadens optical phonons, while surface exchange disorder suppresses acoustic magnon velocities. Molecular dynamics captures size-dependent phonon renormalization, and a reduced-exchange spin-wave model reproduces the magnon behavior. These results establish confinement as a powerful route to tailor spin dynamics and thermal transport in magnetic nanomaterials.