Full flux-closure domains are microscopic topological phenomena found in ferroelectric thin films that feature distinct electric polarization properties. These closed-loop domains have garnered attention among researchers studying new ferroelectric devices, ranging from data storage components and spintronic tunnel junctions to ultra-thin capacitors. However, scientists generally have thought that oxide electrodes would destabilize flux-closure domains.

A research team with leading scientists of Prof. MA Xiuliang, Prof. ZHU Yinlian from Institute of Metal Research of the Chinese Academy of Sciences (IMR, CAS) recently fabricated periodic arrays of flux-closure domains in ferroelectric thin films with oxide electrodes.

Based on their previous studies, the above team consequently anticipated that similar phenomenon might also occur in PTO/electrode systems. They grew PTO films sandwiched between symmetric oxide electrodes on GSO substrates using pulsed laser deposition.

Two types of oxide electrodes are used in the experiments: one based on strontium ruthenate, the other based on lanthanum strontium manganite, chosen as oxide electrodes because of their similar perovskite structures, which work well in layer-by-layer film growth.

Scientists found that periodic flux-closure arrays can be stabilized in PTO films when the top and bottom electrodes are symmetric, while alternating current domains appear when they apply asymmetric electrodes.

It is believed that this work will shed light on understanding the nature of flux-closure domains in ferroelectrics, and open research possibilities in the evolution of these structures under external electric fields.

The findings are reported as the cover article in Applied Physics Letters with the title of "Controlled Growth and Atomic-Scale Mapping of Charged Heterointerfaces in PbTiO3/BiFeO3 Bilayers".

Flux-closures in a PTO film with top and bottom SRO oxide electrodes grown on the GSO (110) substrate (Image by IMR)