Abstract

Abstract
Orthorhombic TbMn2O5 (o-TMO) is a well-known multiferroic manganite with the remarkable property of polarization switching at 3 K under a bias magnetic (H) field along the a axis of Pb21m. To theoretically account for this outstanding observation, we have proposed a modulated spin structure under the saturated bias H field by
considering the relative strength of the three relevant exchange parameters in o-TMO. The proposed modulated structure based on density-functional theory (DFT) calculations is described in terms of the spin angle φ between the neighboring Mn4+-Mn3+ spin moments on the a-b plane. We have shown that the computed DFT polarization plotted as a function of φ satisfactorily accounts for the observed H-field-induced polarization switching. We have further theoretically shown that the square of the critical field strength (Hc) needed for the polarization switching is inversely proportional to the degree of the extrinsic magnetoelectric coupling. The computed partial charge density demonstrates that the H-field-induced polarization switching also accompanies with the switching in the sign of the excess valence-electron densit