We report on theoretical and experimental investigation of A-site-driven ferroelectricity in ferromagnetic La2NiMnO6 thin films grown on SrTiO3 substrates. Structural analysis and density-functional theory calculations show that epitaxial strain stretches the rhombohedral La2NiMnO6 crystal lattice along the cubic direction, triggering a displacement of the A-site La ions in the double-perovskite lattice. The lattice distortion and the A-site displacements stabilize a ferroelectric polar state in ferromagnetic La2NiMnO6 crystals. The ferroelectric state only appears in the rhombohedral La2NiMnO6 phase, where MnO6 and NiO6 octahedral tilting is inhibited by the threefold crystal symmetry. Electron localization mapping showed that covalent bonding with oxygen and 6s orbital lone-pair formation are negligible in this material.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2015 Apr 20|