  Domain wall propagation in modulated-diameter cylindrical nanowires is a key
phenomenon to be studied with a view to designing three-dimensional magnetic
memory devices. This paper presents a theoretical study of transverse domain
wall behavior under the influence of a magnetic field within a cylindrical
nanowire with diameter modulations. In particular, domain wall pinning close to
the diameter modulation was quantified, both numerically, using finite element
micromagnetic simulations, and analytically. Qualitative analytical model for
gently sloping modulations resulted in a simple scaling law which may be useful
to guide nanowire design when analyzing experiments. It shows that the domain
wall depinning field value is proportional to the modulation slope.
