  We have studied the Co layer thickness dependences of magnetocrystalline
anisotropy (MCA), Dzyaloshinskii-Moriya interaction (DMI), and orbital moment
anisotropy (OMA) in W/Co/Pt trilayers. We find the MCA favors magnetization
along the film normal and monotonically increases with decreasing effective
magnetic layer thickness ($t_\mathrm{eff}$). The magnitude of the
Dzyaloshinskii-Moriya exchange constant ($|D|$) increases with decreasing
$t_\mathrm{eff}$ until $t_\mathrm{eff} \sim$1 nm, below which $|D|$ decreases.
MCA and $|D|$ scale with $1/t_\mathrm{eff}$ for $t_\mathrm{eff}$ larger than
$\sim$1.0 nm, indicating an interfacial origin. To clarify the cause of the
$t_\mathrm{eff}$ dependences of MCA and DMI, the OMA of Co in W/Co/Pt trilayers
is studied using x-ray magnetic circular dichroism (XMCD). We find non-zero OMA
when $t_\mathrm{eff}$ is smaller than $\sim$0.8 nm. The OMA increases with
decreasing $t_\mathrm{eff}$ at a rate that is larger than what is expected from
the MCA and Bruno's formula, indicating that other factors contribute to the
MCA at small $t_\mathrm{eff}$ to break the $1/t_\mathrm{eff}$ scaling. The
$t_\mathrm{eff}$ dependence of the OMA also suggests that $|D|$ at
$t_\mathrm{eff}$ smaller than $\sim$1 nm is independent of the OMA at the
interface. We consider the growth of Co on W results in a strain that reduces
the interfacial MCA and DMI at small $t_\mathrm{eff}$, indicating the
importance of lattice structure to control their properties.
