  The properties of Dirac electrons in a magnetic superlattice (SL) on graphene
consisting of very high and thin (delta-function) barriers are investigated. We
obtain the energy spectrum analytically and study the transmission through a
finite number of barriers. The results are contrasted with those for electrons
described by the Schrodinger equation. In addition, a collimation of an
incident beam of electrons is obtained along the direction perpendicular to
that of the SL. We also highlight the analogy with optical media in which the
refractive index varies in space.
