Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

All together now

10.08.2009
Mutual controllability of electricity and magnetism in a weak magnetic material points the way to low-power electronics

Conventional electronic devices use the flow of electrons to process and transmit information throughout the conducting and semiconducting circuits of a computer chip, which requires external power.

Scientists are striving to decrease this demand by electrically controlling a property of the electron called spin, which is the source of magnetization. Making so-called ‘spintronic chips’ from multiferroics, a new class of materials with strongly coupled ferroelectric and ferromagnetic properties, could enable electrical control of magnetization.

Yusuke Tokunaga from the RIKEN Advanced Science Institute, Wako and his colleagues have now discovered that the well-known ferromagnet gadolinium iron oxide (GdFeO3) is also ferroelectric and that its ferromagnetic and ferroelectric properties are strongly coupled.1. This means that new multifunctional devices based on this material are now a possibility, and could operate with much less power than their conventional counterparts.

A tale of two properties

Ferromagnetism and ferroelectricity, which rarely occur in the same material, arise from different physical processes.

Ferromagnetism occurs in materials, such as iron, below a certain temperature (the Curie temperature), and the magnetic moments of regions of atoms, called ferromagnetic domains, align to point in the same direction when placed in a strong magnetic field (Fig. 2). This alignment remains once the field is removed. Most common magnetic materials are ferromagnetic, including those used to store information electronically.

Ferroelectricity, on the other hand, occurs in materials in which oppositely charged atoms form regions of locally aligned dipoles, and the net polarity can be aligned by a strong electric field (Fig. 3). As with ferromagnetism, this polarization remains once the field is removed.

If the ferromagnetic and ferroelectric properties of a multiferroic material are linked, or coupled, they can be manipulated simultaneously, which would allow the development of multifunctional components. Indeed, the discovery by Tokunaga and co-workers of the multiferroic properties of GdFeO3 began with a series of materials that barely exhibited either property.

“We are always searching for new multiferroics,” says Tokunaga. “We started our search with the perovskite ortho-aluminate, DyAlO3. This material is known to be magnetoelectric, but in the absence of any applied field is neither ferromagnetic nor ferroelectric.”

Powerful combination for low-power electronics

Magnetoelectric materials, such as DyAlO3, are crystals in which charge polarization can be induced with a magnetic field as well as an electric field. In previous work, Tokunaga and co-workers tried substituting the aluminum (Al) atoms in this material with iron (Fe) atoms.2. They found that it did become weakly ferromagnetic and ferroelectric, but only while it was held in a magnetic field—when the field was removed both characteristics disappeared.

“As a next step, we searched for a material with the same magnetic structure as DyFeO3 in an applied field,” explains Tokunaga. Since the researchers knew that the arrangement and orientation of the magnetic moments of GdAlO3 are the same as those of DyAlO3, they suspected that GdFeO3 might be able to support a similar magnetic structure to that of the magnetic field-induced multiferroic state of DyFeO3, but without the need for a magnetic field.

When the researchers grew large crystals of GdFeO3 and measured their properties, they found that this material was indeed both ferroelectric and ferromagnetic without any applied field. Moreover, they discovered that its ferroelectric and ferromagnetic properties were intrinsically linked and its polarization could be altered with a magnetic field. But more significantly, they revealed that its magnetization could be changed with an electric field—a property that is particularly useful for making low-power electronics.

“Current-induced magnetization reversal is intensively studied as a means of making devices that use the spin of electrons, as well as their charge, for processing information,” notes Tokunaga. However, the metallic and semiconducting materials used in these devices require the flow of current, which dissipates energy. “The great advantage of multiferroic insulators, such as GdFeO3, is that their magnetization can be changed by an electric field with almost zero current and very little energy loss,” he says.

Composite domain walls

Interactions between the so-called domain walls, or boundaries between regions of different magnetization and polarization in a material, cause the coupling the ferromagnetic and ferroelectric properties of GdFeO3, according to the researchers.

When a strong magnetic field is applied to a ferromagnetic material, the changes in alignment of its magnetic moments occur gradually through the growth of smaller aligned regions, or domains. As they grow, the domain walls push through the material and, eventually, all the moments of the material align in the direction of the magnetic field. A similar process occurs to the electric dipoles of a ferroelectric when its polarization is switched in response to an electric field.

In a multiferroic material, ferromagnetic and ferroelectric domain walls can exist at different points of the material. A collision between these walls in GdFeO3 can result in the formation of a composite multiferroic domain wall that switches both the magnetization and the polarization of the material as it moves. Moreover, when a composite wall hits a defect in the material, it can decouple to form separate ferromagnetic and ferroelectric walls once more. The merging, propagation and separation of the walls allows the material’s magnetization to be switched with an electric field, and allows its polarization to be switched with a magnetic field.

The multiferroic behavior of GdFeO3 occurs only at temperatures below 2.5 K (-270.65 °C), so the researchers plan to search for materials that behave similarly at much higher temperatures. If successful, their endeavor will bring novel practical electronic devices a step closer to realization.

Reference

1. Tokunaga, Y., Furukawa, N., Sakai, H., Taguchi, Y., Arima, T. & Tokura, Y. Composite domain walls in a multiferroic perovskite ferrite. Nature Materials 8, 558–562 (2009).

2. Tokunaga, Y., Iguchi, S., Arima, T. & Tokura, Y. Magnetic-field-induced ferroelectric state in DyFeO3. Physical Review Letters 101, 087205 (2008).

The corresponding author for this highlight is based at the RIKEN Cross-Correlated Materials Research Group, Exploratory Materials Team

About the Author

Yusuke Tokunaga

Yusuke Tokunaga was born in Tokyo, Japan, in 1977. He graduated from Department of Applied Physics, the University of Tokyo, in 2000, and obtained his PhD in 2005 from the same university. Since then, he has been working as a postdoctoral researcher. After spending two years at ERATO Tokura Spin Superstructure Project, JST, he moved to ERATO Tokura Multiferroics Project, JST. His working place was changed from AIST, Tsukuba, Japan to RIKEN in 2008. He is now working as a visiting researcher at the RIKEN Advanced Science Institute. His current area of interest is in strongly correlated electron systems including multiferroics.

Journal information

Tokunaga, Y., Furukawa, N., Sakai, H., Taguchi, Y., Arima, T. & Tokura, Y. Composite domain walls in a multiferroic perovskite ferrite. Nature Materials 8, 558–562 (2009), . Tokunaga, Y., Iguchi, S., Arima, T. & Tokura, Y. Magnetic-field-induced ferroelectric state in DyFeO3. Physical Review Letters 101, 087205 (2008).

Saeko Okada | Research asia research news
Further information:
http://www.rikenresearch.riken.jp/research/758/

More articles from Power and Electrical Engineering:

nachricht Researchers use light to remotely control curvature of plastics
23.03.2017 | North Carolina State University

nachricht TU Graz researchers show that enzyme function inhibits battery ageing
21.03.2017 | Technische Universität Graz

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>