  High precision skyrmion pinning by an intentionally created magnetic
structure is important in skyrmion manipulation. Here, we consider skyrmion
pinning by various types of disks. Among other findings, we clarify that, in
terms of pinning position and pinning potential landscape, one needs to
distinguish thin-wall skyrmions from thick-wall skyrmions because of
fundamental differences. A skyrmion wall prefers areas with a weaker exchange
stiffness, a larger DMI constant, or a smaller magnetic anisotropy while a
skyrmion core experiences only the magnetic anisotropy, not exchange stiffness
and DMI. Depending on disk type, skyrmion type, and the relative size of the
disk (to skyrmion), a skyrmion can be pinned at the symmetric (center) or
asymmetric (off-center) point of a disk. In case a skyrmion is pinned by a
local energy minimum, thermal agitation can depin the skyrmion, and the pinning
lifetime follows an Arrhenius law. Interestingly, when the disk size is
comparable to the skyrmion size, the skyrmion deforms greatly such that the
skyrmion will shrink or expand to fill the whole disk. These findings should be
important for skyrmion manipulations.

Mesoscale and Nanoscale Physics