发表机构
Cornell University; The Pennsylvania State University; Leibniz-Institut für Kristallzüchtung; Oak Ridge National Laboratory; University of Tennessee; University of California, Berkeley; University of North Texas; University of Southern California; Kavli Institute at Cornell for Nanoscale Science（康奈尔大学; 宾夕法尼亚州立大学; 莱布尼兹晶体生长研究所; 橡树岭国家实验室; 田纳西大学; 加州大学伯克利分校; 北德克萨斯大学; 南加州大学; 康奈尔纳米科学卡弗里研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过外延应变在BaFe12O19薄膜中实现室温极性有序，结合实验与模拟证实其成为弛豫多铁体，为设计室温多铁材料提供新路径。
AI 中文摘要
在室温下同时具有磁有序和电有序的多铁性材料十分罕见。在此，我们展示了亚铁磁性六方铁氧体BaFe12O19中应变诱导的室温极性有序。第一性原理计算揭示了一个具有多种竞争偶极构型的应变可调能量景观，并预测压应变有利于极性畸变。利用同构的Sr1.03Ga10.81Mg0.58Zr0.58O19衬底，我们生长了具有1.1%面内双轴压缩的共格应变BaFe12O19薄膜。二次谐波产生测量证明了反演对称性破缺，并确立了一种至少持续到1000 K的应变稳定极性相。多切片电子叠层衍射直接揭示了应变薄膜中三角双锥位点内Fe3+离子增强的偏心位移以及空间变化的局域极化，证明了极性纳米区域的形成。路径积分蒙特卡洛模拟进一步表明，压应变抑制了量子涨落并稳定了这些局域极性畸变。总之，这些结果确立了应变工程化的BaFe12O19作为一种室温弛豫多铁体，其中稳健的亚铁磁性与纳米尺度的极性有序共存。我们的工作展示了一条通过外延应变将潜在铁电亚铁磁体转变为极性磁性材料的途径。
英文摘要
Multiferroic materials that combine magnetic and electric order at room temperature are rare. Here, we demonstrate strain-induced room-temperature polar order in the ferrimagnetic hexaferrite BaFe12O19. First-principles calculations reveal a strain-tunable energy landscape with multiple competing dipolar configurations and predict that compressive strain favors polar distortions. Using an isostructural Sr1.03Ga10.81Mg0.58Zr0.58O19 substrate, we grow coherently strained BaFe12O19 films with 1.1% in-plane biaxial compression. Second-harmonic generation measurements demonstrate inversion-symmetry breaking and establish a strain-stabilized polar phase that persists to at least 1000 K. Multislice electron ptychography directly reveals enhanced off-centering of Fe3+ ions within the trigonal-bipyramidal sites of the strained films and spatially varying local polarization, demonstrating the formation of polar nanoregions. Path-integral Monte Carlo simulations further show that compressive strain suppresses quantum fluctuations and stabilizes these local polar distortions. Together, these results establish strain-engineered BaFe12O19 as a room-temperature relaxor multiferroic, in which robust ferrimagnetism coexists with nanoscale polar order. Our work demonstrates a route for transforming an incipient ferroelectric ferrimagnetic into a polar magnetic material through epitaxial strain.
