  Azimuthal anisotropies of muons from charm and bottom hadron decays are
measured in Pb+Pb collisions at $\sqrt{s_\mathrm{NN}}= 5.02$ TeV. The data were
collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2018
with integrated luminosities of $0.5~\mathrm{nb}^{-1}$ and
$1.4~\mathrm{nb^{-1}}$, respectively. The kinematic selection for heavy-flavor
muons requires transverse momentum $4 < p_\mathrm{T} < 30$ GeV and
pseudorapidity $|\eta|<2.0$. The dominant sources of muons in this
$p_\mathrm{T}$ range are semi-leptonic decays of charm and bottom hadrons.
These heavy-flavor muons are separated from light-hadron decay muons and
punch-through hadrons using the momentum imbalance between the measurements in
the tracking detector and in the muon spectrometers. Azimuthal anisotropies,
quantified by flow coefficients, are measured via the event-plane method for
inclusive heavy-flavor muons as a function of the muon $p_\mathrm{T}$ and in
intervals of Pb+Pb collision centrality. Heavy-flavor muons are separated into
contributions from charm and bottom hadron decays using the muon transverse
impact parameter with respect to the event primary vertex. Non-zero elliptic
($v_{2}$) and triangular ($v_{3}$) flow coefficients are extracted for charm
and bottom muons, with the charm muon coefficients larger than those for bottom
muons for all Pb+Pb collision centralities. The results indicate substantial
modification to the charm and bottom quark angular distributions through
interactions in the quark-gluon plasma produced in these Pb+Pb collisions, with
smaller modifications for the bottom quarks as expected theoretically due to
their larger mass.
