  Spin waves are the low-energy excitations of magnetically ordered materials.
They are key elements in the stability analysis of the ordered phase and have a
wealth of technological applications. Recently, we showed that spin waves of a
magnetic nanowire may carry a definite amount of orbital angular momentum
components along the propagation direction. This helical, in addition to the
chiral, character of the spin waves is related to the spatial modulations of
the spin wave phase across the wire. It, however, remains a challenge to
generate and control such modes with conventional magnetic fields. Here, we
make the first proposal for a \textit{magnetic} spiral phase plate by
appropriately synthesizing two magnetic materials that have different speeds of
spin waves. It is demonstrated with full-numerical micromagnetic simulations
that despite the complicated structure of demagnetization fields, a homogeneous
spin wave passing through the spiral phase plate attains the required twist and
propagates further with the desired orbital angular momentum. While excitations
from the ordered phase may have a twist, the magnetization itself can be
twisted due to internal fields and forms what is known as a magnetic vortex. We
point out the differences between both types of magnetic phenomena and discuss
their possible interaction.
