Magnetic response of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Sr</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>RuO</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>: Quasi-local spin fluctuations due to Hund's coupling

We study the magnetic susceptibility in the normal state of ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ using dynamical mean-field theory including dynamical vertex corrections. Besides the well-known incommensurate response, our calculations yield quasi-local spin fluctuations which are broad in momentum and centered around the $\mathrm{\ensuremath{\Gamma}}$ point, in agreement with recent inelastic neutron-scattering experiments [Steffens et al., Phys. Rev. Lett. 122, 047004 (2019)]. We show that these quasi-local fluctuations are controlled by the Hund's coupling and account for the dominant contribution to the momentum-integrated response. Although all orbitals contribute equally to the incommensurate response, the enhanced $\mathrm{\ensuremath{\Gamma}}$-point response originates from the planar $xy$ orbital.