(Top) Schematic representation of obtaining polarized metallic states using a flexoelectric field (bottom) Atomic-scale imaging of the polarized metal SrRuO3. Credit: POSTECH
In the field of materials science, the phenomena of polarization and polarity are traditionally associated with insulators. However, let’s imagine a scenario in which these characteristics could be induced in metals, potentially mitigating the power losses attributed to semiconductors and extending the life of batteries built into electronic devices.
A recent advance achieved through the collaborative efforts of South Korean researchers is the discovery of a method to induce and control polarization and polarity states within metals. Their study was published in Natural physics on January 17, 2024.
Free electrons in metals exhibit unrestricted movement, making it difficult to align them in specific directions in order to induce polarization or polarity states. In addition, the symmetrical structure at both ends of metal crystals has always posed problems in inducing these electrical effects.
The research team used flexoelectric fields to implement polarization and polarity states in metals. This type of field appears when the surface of an object undergoes non-uniform deformation, allowing manipulation of the movement of charges and electrical characteristics by subtly changing the lattice structure of metals.
The team applied external pressure to the widely used strontium ruthenate (SrRuO3) in the field of electronic components and semiconductors, generating a flexoelectric field. This metal oxide, characterized by heteroepitaxy, where strontium and ruthenium oxide crystals of different shapes grow in the same direction, has a centrosymmetric structure.
The flexoelectric field altered the electronic interactions and lattice structure within strontium ruthenate, leading to successful induction of polarization within the metal, causing a transformation of its electrical and mechanical properties and breaking the central symmetric structure. Using flexoelectric polarization and control of a ferromagnetic metal, the research team managed to unravel the mystery surrounding the implementation of polarization and polarity within metallic substances.
The study’s lead researcher, Professor Daesu Lee from the Department of Physics at Pohang University of Science and Technology (POSTECH), said: “We are the first researchers to verify the universal implementation of polarity states within metallic substances. I hope that the results of this study will prove beneficial for the creation of highly efficient devices in the fields of semiconductors and electricity.
More information:
Wei Peng et al, Flexoelectric polarization and control of a ferromagnetic metal, Natural physics (2024). DOI: 10.1038/s41567-023-02333-8
Provided by Pohang University of Science and Technology
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