Periodic Giant Polarization Gradients in Doped BiFeO3 Thin Films

Journal Article

Campanini, M., R. Erni, C.-H. Yang, Ramamoorthy Ramesh, M.D. Rossell

10.1021/acs.nanolett.7b03817

The ultimate challenge for the development of new multiferroics with enhanced properties lies in achieving nanoscale control of the coupling between different ordering parameters. In oxide-based multiferroics, substitutional cation dopants offer the unparalleled possibility to modify both the electric and magnetic properties at a local scale. Herein it is demonstrated the formation of a dopant-controlled polar pattern in BiFeO3 leading to the spontaneous instauration of periodic polarization waves. In particular, nonpolar Ca-doped rich regions act as spacers between consecutive dopant-depleted regions displaying coupled ferroelectric states. This alternation of layers with different ferroelectric state creates a novel vertical polar structure exhibiting giant polarization gradients as large as 70 μC cm-2 across 30 Å thick domains. The drastic change in the polar state of the film is visualized using high-resolution differential phase-contrast imaging able to map changes in ferroelectric polarization at atomic scale. Furthermore, a periodic distortion in the Fe - O - Fe bonding angle suggests a local variation in the magnetic ordering. The findings provide a new insight into the role of doping and reveal hitherto unexplored means to tailor the functional properties of multiferroics by doping engineering. © 2018 American Chemical Society.

Nano Letters

18

2018

15306984

cited By 15

Ramesh Lab