EuAl2at pressures up to 41 GPa: A localized magnet exhibiting highly nonlinear electronic effects

${}_{}{}^{151}{}_{}{}^{}\mathrm{Eu}$ Mössbauer studies under hydrostatic pressures up to 41 GPa coupled to x-ray diffraction measurements show that—contrary to expectations—the 4f electrons in ${\mathrm{EuAl}}_2$ remain fully localized even under a reduction of unit cell volume of ∼30%. However, strongly nonlinear effects are observed for the conduction electron polarization, for the s-electron density ρ(0) at the ${}_{}{}^{151}{}_{}{}^{}\mathrm{Eu}$ nucleus, the Néel temperature ${\mathit{T}}_{\mathit{N}}$, and the transferred hyperfine field hyperbolically; ${\mathit{T}}_{\mathit{N}}$ and ${\mathit{B}}_{\mathrm{thf}}$ connected to ρ(0). The latter results can be described quantitatively within the RKKY formalism.