  The iron-based superconductors had a significant impact on condensed matter
physics. They have a common structural motif of a two-dimensional square iron
lattice and exhibit fruitful physical properties as a strongly correlated
electron system. During the extensive investigations, quasi-one-dimensional
iron-based spin-ladder compounds attracted much attention as a platform for
studying the interplay between magnetic and orbital ordering. In these
compounds, BaFe2S3 and BaFe2Se3 were found to exhibit superconductivity under
high pressure, having a different crystal and magnetic structure at low
temperature. We report a brief review of the iron-based spin-ladder compound
and recent studies for BaFe2+d(S1-xSex)3. BaFe2(S0.75 Se0.25)3 is in the
vicinity of the boundary of two different magnetic phases and it is intriguing
to perform high pressure experiments for studying superconductivity, since
effects of large magnetic fluctuations on superconductivity are expected. The
effect of iron stoichiometry on the interplay between magnetism and
superconductivity is also studied by changing the iron concentration in
BaFe2+dSe3.
