  Frustrated magnets are known to support two-dimensional topological solitons,
called skyrmions. A continuum model for frustrated magnets has recently been
shown to support both two-dimensional skyrmions and three-dimensional knotted
solitons (hopfions). In this note we derive lower bounds for the energies of
these solitons expressed in terms of their topological invariants. The bounds
are linear in the degree in the case of skyrmions and scale as the Hopf degree
to the power 3/4 in the case of hopfions.
