Enhanced polarization and magnetoelectric response in Tb1−x Ho x MnO3

A series of manganites Tb(1-x) Ho (x) MnO(3) (0a parts per thousand currency signxa parts per thousand currency sign0.6) with orthorhombic structure are synthesized and detailed investigations on their multiferroicity are performed. Successive magnetic transitions upon temperature variation are evidenced for all the samples, and both the Mn(3+)spiral spin ordering and rare-earth spin ordering are suppressed with increasing x. A significant enhancement of both the polarization and magnetoelectric response within 0.2 < x < 0.4 is observed, which may probably result from the shortening of the spiral-spin-ordering period, due to the competition between the spiral spin order and E-type antiferromagnetic order. This argument is supported by further theoretical calculations based on the two e (g) -orbital double-exchange model.