  The phase diagram of quarter-hole-doped perovskite manganites is investigated
using the doubleexchange model. An exotic striped type-II multiferroic phase,
where 25% of the nearest-neighbor spin couplings are orthogonal to each other,
is found in the narrow-bandwidth region. Comparing with the spiral-spin
ordering phase of undoped manganites, the multiferroic Curie temperature of the
new phase is estimated to be ~4 times higher, while the ferroelectric
polarization is similar in magnitude. Our study provides a path for
noncollinear spin multiferroics based on electronic self-organization,
different from the traditional approach based on superexchange frustration.
