Enhanced polarization, magnetoelectric response and possible bi-multiferroic phase separation in Tb_{1-x}Ho_xMnO_3

[Abstract] A series of manganites Tb 1- x Ho x MnO 3 (0 ≤ x ≤ 0.6) with orthorhombic structure are synthesized and detailed investigations on their multiferroicity are performed. Successive magnetic transitions upon temperature variation are evidenced for all samples, and both the Mn 3+ spiral spin ordering and rare-earth spin ordering are suppressed with increasing x . Significant enhancement of both the polarization and magnetoelectric response within 0.2< x <0.4 is observed, which may be ascribed to the competition possibly existing between spiral and E -type spin orders. Theoretical calculation is given based on two e g -orbital double-exchange model, and the result supports the scenario of the multiferroic phase separation.