  Current scenario in multiferroics demands a breakthrough discovery of
promising materials after BiFeO3. Recently, the controversial discovery of room
temperature ferroelectricity (FE) in SmFeO3 [PRL 107, 117201 (2011); 113,
217203 (2014)] inspires the investigation of HoFeO3. Here, we report a natural
ferroelectric order below 210 K (TFE) along c-axis with reasonably large
polarization and low-field strong magnetoelectric coupling. Synchrotron and
neutron diffraction results confirm that a shift of O atoms along c-axis of
polar Pbn21 structure causes FE in HoFeO3. The exchange striction mechanism is
suggested to elucidate the ferroelectric order. The results create a renewed
attention for searching promising candidates with a natural ferroelectric order
and higher TFE in the rest of the RFeO3 series.
