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 Silicon solar cell of ISFH yields 25% efficiency with passivating POLO contacts
08.12.2016 | Institut für Solarenergieforschung GmbH

nachricht Robot on demand: Mobile machining of aircraft components with high precision
06.12.2016 | Fraunhofer IFAM

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: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>