  We show that an individual adatom on a magnetic surface can exhibit a
noncollinear spin density. Using density functional theory we study Co and Ir
adatoms on a Mn monolayer on the W(110) surface which possesses a noncollinear
canted spin structure. Due to hybridization with the nearest and next-nearest
Mn atoms of the monolayer the spin direction of the underlying substrate is
encoded into the orbitals of the adatom. This explains recent scanning
tunneling microscopy experiments showing a spin sensitive shape asymmetry of
adatoms [Serrate \emph{et al.}, Phys. Rev. B \textbf{93}, 125424 (2016)] which
confirms the intra-atomic noncollinear magnetism of the adatoms.
