摘要
We report the structural, magnetic, and ferroelectric properties of double-perovskite Bi 2 FeMnO 6 in which Fe 3+ and Mn 3+ cations are present with alternative ordering along the [111] direction. High-flux synchrotron X-ray diffraction and high resolution transmission electron microscopy show that the pseudo-cubic lattice of Bi 2 FeMnO 6 consists of alternatively corner-shared octahedra of FeO 6 and MnO 6 . In the highly ordered Bi 2 FeMnO 6 thin films, the unusual spin-glassy magnetic state is observed below 18 K by a superconducting quantum interference device, and this is ascribed to the magnetic frustration at the [111] Fe 3+ and Mn 3+ planes as indicated by X-ray magnetic circular dichroism measurements. Combining with the orbital model analysis based on Goodenough-Kanamori-Anderson rules, first-principles calculations and Monte Carlo simulations suggest that magnetic frustration is dominated by the long-range second nearest neighboring antiferromagnetic interactions of Fe 3+ -Fe 3+ and Mn 3+ -Mn 3+ and leads to the surprisingly weak magnetism. On the other hand, robust room-temperature ferroelectricity in Bi 2 FeMnO 6 films is confirmed by piezoelectric force microscopy through electrically switching the polarization state and the ferroelectric retention.