ATLAS measurements of $CP$ violation and rare decay processes with beauty mesons

The ATLAS experiment has performed measurements of $B$-meson rare decays proceeding via suppressed electroweak flavour changing neutral currents, and of mixing and $CP$ violation in the neutral $B_s$ meson system. This talk will focus on the latest results from the ATLAS collaboration, such as rare processes $B^0_s \rightarrow \mu\mu$ and $B^0 \rightarrow \mu\mu$, and $CP$ violation in the $B^0_s \rightarrow J/\psi\phi$ decays. In the latter, the Standard Model predicts the $CP$ violating mixing phase, $\phi_s$, to be very small and its SM value is very well constrained, while in many new physics models large $\phi_s$ values are expected. The latest measurements of $\phi_s$ and several other parameters describing the $B^0_s \rightarrow J/\psi\phi$ decays will be reported.