Vacancies' effect on the ferroelectric and magnetic response of Eu‐doped Bi_0.85Pr_0.15Fe_0.97Mn_0.03O₃ thin films

Abstract

Polycrystalline‐multiferroic Bi0.85Pr0.15‐xEuxFe0.97Mn0.03O3 (0, 0.01, 0.02, 0.03, 0.4, 0.05) thin films were grown on fluorine‐doped tin oxide (FTO)/glass substrate with radio frequency (RF) magnetron sputtering. Rietveld quantitative analysis reveals that whereas the starting materials (nanoparticles [NPs] and ceramics) are composed of tetragonal P4italicmm symmetry, the thin films can lose 80% of this symmetry to become rhombohedral R3c symmetry. The structure evolution from tetragonal to rhombohedral symmetry indicates that the Eu3+ ion acts positively to reduce the tensile residual stress component from 24 to 1.8 MPa in the thin films. The band gap shifts to 2.17 eV by Eu substitution at the A‐site of the perovskite. Scanning electron microscopy (SEM) results show high‐elongated nanocrystals that share parallel facets without porosity. In that morphology, the Eu has a strong influence on reducing the magnetic coercivity from 10.7 to 6.5 kOe, which has been interpreted in terms of local shape anisotropy. Although the magnetic response increases monotonously, the ferroelectric polarization decreases with doping. These changes are explained through local defects created by the evolution of the VO·· concentration that changes significantly by Eu doping.