Heavy Mn-doping effect on spontaneous polarization in ferroelectric BiFeO3 thin films

Abstract

Mn doping effect on the crystal structure and spontaneous polarization (Ps) in ferroelectric BiFeO3 (BFO) thin films are experimentally and theoretically investigated. Polarization hysteresis measurements for BiFe1−xMnxO3 (BFMO) films grown on (100) SrTiO3 substrates with SrRuO3 electrodes indicate that remanent polarization (Pr) remains unchanged in the range of 0 ≤ x ≤ 0.1. As a result of the density-functional theory (DFT) calculations for the rhombohedral, tetragonal, and monoclinic phases of BFO and BFMO (x = 0.5), we find that the monoclinic phase with compressive strain from the substrates yields the most reasonable Ps. The DFT calculations also indicate that heavy doping of up to 50% Mn does not lead to a considerable deterioration in Ps, which is consistent with the experiments. Our investigations demonstrate that the ferroelectric polarization in the BFMO system can be retained for a wide range of Mn content either in bulk or thin-film form.