Tearing down the barriers to domain wall electronics

Manipulating domains within ferroelectric semiconductors has attracted attention in recent years for potentially allowing domains and domain walls to be used as functional elements in nanoelectronics. One type of multiferroic material, hexagonal manganites, has shown particular potential because of their unusual, improper ferroelectric properties. Reporting its work in Applied Physics Letters, a team of scientists has made strides in understanding one such material, hexagonal erbium manganite (h-ErMnO₃).

Researchers have investigated electric-field poling of the geometric-driven improper ferroelectric h-ErMnO₃. From a detailed dielectric analysis, they have deduced the temperature- and frequency-dependent range for which single-crystalline h-ErMnO₃ exhibits purely intrinsic dielectric behavior. This provides the first comprehensive experimental study addressing the switching dynamics in hexagonal manganites.

Below the ferroelectric transition temperature, hexagonal manganites display geometrically driven improper ferroelectricity with six possible domain states, forming a predefined polar pattern and stable vortexlike topological defects where their domain walls meet.

By cooling ErMnO₃ to as low as 100 kelvins, the team was able to study the temperature-dependent dielectric properties and the material’s hysteresis loops, revealing a theoretically predicted saturation polarization in the order of 5 to 6 µC/cm².

Using a model based on Ishibashi-Orihara theory for domain wall movement in proper ferroelectrics, the group found that the frequency-dependent evolution of the coercive field followed a simple power law that was in perfect agreement to values of proper ferroelectrics showing pure domain wall movement. This approach, they concluded, enables the electric field control of domain walls in the improper ferroelectric manganites.

The group said they hope their work will bring us closer to use improper ferroelectrics for domain wall-based electronics.

Source: “Frequency dependent polarisation switching in h-ErMnO₃,” by Alexander Ruff, Ziyu Li, Alois Loidl, Jakob Schaab, Manfred Fiebig, Andres Cano, Zewu Yan, Edith Bourret, Julia Glaum, Dennis Meier, and Stephan Krohns, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5026732 .