Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Understanding the mechanism for generating electric current without energy consumption at room temperature

28.12.2015

A group of researchers in Japan and China identified the requirements for the development of new types of extremely low power consumption electric devices by studying Cr-doped (Sb, Bi)2Te3 thin films. This study has been reported in Nature Communications.

At extremely low temperatures, an electric current flows around the edge of the film without energy loss, and under no external magnetic field. This attractive phenomenon is due to the material's ferromagnetic properties; however, so far, it has been unclear how the material gains this property. For the first time, researchers have revealed the mechanism by which this occurs.


Ferromagnetism mediated by Sb or Te atoms

(Credit: Hiroshima University)

“Hopefully, this achievement will lead to the creation of novel materials that operate at room temperature in the future,” said Akio Kimura, a professor at Hiroshima University and a member of the research group.

Their achievement can be traced back to the discovery of the quantum Hall effect in the 1980’s, where an electric current flows along an edge (or interface) without energy loss. However, this requires both a large external magnetic field and an extremely low temperature. This is why practical applications have not been possible. Researchers believed that this problem could be overcome with new materials called topological insulators that have ferromagnetic properties such as those found in Cr-doped (Sb, Bi)2Te3.

A topological insulator, predicted in 2005 and first observed in 2007, is neither a metal nor an insulator, and has exotic properties. For example, an electric current is generated only at the surface or the edge of the material, while no electric current is generated inside it. It looks as if only the surface or the edge of the material has metallic properties, while on the inside it is an insulator.

At extremely low temperatures, a thin film made of Cr-doped (Sb, Bi)2Te3 shows a peculiar phenomenon. As the film itself is ferromagnetic, an electric current is spontaneously generated without an external magnetic field and electric current flows only around the edge of the film without energy loss. However, it was previously unknown as to why Cr-doped (Sb, Bi)2Te3 had such ferromagnetic properties that allowed it to generate electric current.

“That’s why we selected the material as the object of our study,” said Professor Kimura.

Because Cr is a magnetic element, a Cr atom is equivalent to an atomic-sized magnet. The N-S orientations of such atomic-sized magnets tend to be aligned in parallel by the interactions between the Cr atoms. When the N-S orientations of Cr atoms in Cr-doped (Sb, Bi)2Te3 are aligned in parallel, the material exhibits ferromagnetism. However, the interatomic distances between the Cr atoms in the material are, in fact, too long to interact sufficiently to make the material ferromagnetic.

The group found that the non-magnetic element atoms, such as the Sb and Te atoms, mediate the magnetic interactions between Cr atoms and serve as the glue to fix the N-S orientations of Cr atoms that face one direction. In addition, the group expects that its finding will provide a way to increase the critical temperature for relevant device applications.

The experiments for this research were mainly conducted at SPring-8. “We would not have achieved perfect results without the facilities and the staff there. They devoted themselves to detecting the extremely subtle magnetism that the atoms of non-magnetic elements exhibit with extremely high precision. I greatly appreciate their efforts,” Kimura said.

For further information, please contact:

Yujiro Tokumitsu

Hiroshima University

+81-82-424-4397

pr-research@office.hiroshima-u.ac.jp

www.hiroshima-u.ac.jp

 

Full bibliographic information 【Published article】
Ye, M. et al. Carrier-mediated ferromagnetism in the magnetic topological insulator Cr-doped (Sb,Bi)2Te3. Nat. Commun. 6:8913 doi: 10.1038/ncomms9913 (2015).
http://www.nature.com/ncomms/2015/151119/ncomms9913/full/ncomms9913.html

【Authors and their affiliations】
Mao Ye1,2, Wei Li1,2, Siyuan Zhu3, Yukiharu Takeda4, Yuji Saitoh4, Jiajia Wang5, Hong Pan6, Munisa Nurmamat3, Kazuki Sumida3, Fuhao Ji6, Zhen Liu6, Haifeng Yang1, Zhengtai Liu1, Dawei Shen1,2, Akio Kimura3, Shan Qiao1,2,5, and Xiaoming Xie1,2,5
1 State Key Laboratoryof Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences
2 CAS-Shanghai Science Research Center
3 Graduate School of Science, Hiroshima University
4 Condensed Matter Science Division, Quantum Beam Science Center, Japan Atomic Energy Agency
5 School of physical science and technology, ShanghaiTech University
6 Department of Physics, State Key Laboratory of Surface Physics, and Laboratory of Advanced Materials, Fudan University

Yujiro Tokumitsu | AlphaGalileo

More articles from Power and Electrical Engineering:

nachricht Waste from paper and pulp industry supplies raw material for development of new redox flow batteries
12.10.2017 | Johannes Gutenberg-Universität Mainz

nachricht Low-cost battery from waste graphite
11.10.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

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: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>