  We demonstrate that delta-doping can be used to create a dimensionally
confined region of metallic ferromagnetism in an antiferromagnetic (AF)
manganite host, without introducing any explicit disorder due to dopants or
frustration of spins. Delta-doped carriers are inserted into a manganite
superlattice (SL) by a digital-synthesis technique. Theoretical consideration
of these additional carriers show that they cause a local enhancement of
ferromagnetic (F) double-exchange with respect to AF superexchange, resulting
in local canting of the AF spins. This leads to a highly modulated
magnetization, as measured by polarized neutron reflectometry. The spatial
modulation of the canting is related to the spreading of charge from the doped
layer, and establishes a fundamental length scale for charge transfer,
transformation of orbital occupancy and magnetic order in these manganites.
Furthermore, we confirm the existence of the canted, AF state as was predicted
by de Gennes [P.-G. de Gennes, Phys. Rev. 118, 141 (1960)], but had remained
elusive.
