  The multiferroic RMn2O5 family, where R is rare-earth ion or Y, exhibits rich
physics of multiferroicity which has not yet well understood, noting that
multiferroicity is receiving attentions for promising application potentials.
DyMn2O5 is a representative member of this family. The ferroelectric
polarization in DyMn2O5 is claimed to have two anti-parallel components: one
(PDM) from the symmetric exchange striction between the Dy3+-Mn4+ interactions
and the other (PMM) from the symmetric exchange striction between the Mn3+-Mn4+
interactions. We investigate the evolutions of the two components upon a
partial substitution of Mn3+ by nonmagnetic Al3+ in order to tailor the Mn-Mn
interactions and then to modulate component PMM in DyMn2-x/2Alx/2O5. It is
revealed that the ferroelectric polarization can be successfully reversed by
the Al-substitution via substantially suppressing the Mn3+-Mn4+ interactions
and thus the PMM. The Dy3+-Mn4+ interactions and the polarization component PDM
can sustain against the substitution until a level as high as x=0.2. In
addition, the independent Dy spin ordering is shifted remarkably down to an
extremely low temperature due to the Al3+ substitution. The present work not
only confirms the existence of the two anti-parallel polarization components
but also unveils the possibility of tailoring them independently.
