Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists explain how the giant magnetoelectric effect occurs in bismuth ferrite

23.05.2016

Scientists have created a theoretical model which explains a previously little-studied phenomenon -- a giant electromagnetic effect in bismuth ferrite

A team of scientists from the Moscow Institute of Physics and Technology (MIPT), the National Research University of Electronic Technology (MIET), and the Prokhorov General Physics Institute have proposed a theoretical model that explains the unexpectedly high values of the linear magnetoelectric effect in BiFeO3 (bismuth ferrite) that have been observed in a number of experiments. The team also suggested a way of further enhancing the effect. The results of the study have been published in the journal Physical Review B.


Fig. 1. The spin cycloid structure in BiFeO3.

Credit: MIPT press-office

One particular feature of bismuth ferrite is that in bulk samples, spins of Fe3+ iron ions are arranged in the form of a cycloid (Fig. 1). This spin structure can be destroyed by a strong magnetic field or mechanical stress. Without a spin cycloid, bismuth ferrite exhibits a large linear magnetoelectric effect, and this effect was the focal point of the study.

"The theoretical description presented in the paper may be applicable to other multiferroics similar to BiFeO3. This will help in predicting the value of their magnetoelectric effect, which, in turn, will make it easier to find new and promising materials for industrial applications," says the head of MIPT's Laboratory of physics of magnetic heterostructures and spintronics for energy-saving information technologies, Prof. Anatoly Zvezdin.

Multiferroics and the magneto electric effect

Multiferroics are materials that simultaneously exhibit different ferroic orders, including magnetic, ferroelectric and/or ferroelastic. If there is an interaction between electric and magnetic subsystems in a material, a magnetoelectric (ME) effect may occur.

The magnetoelectric effect is when electric polarization occurs under the influence of an external magnetic field and magnetization occurs under the influence of an electric field. This allows an electric field to be used to control the magnetic properties of a material and a magnetic field to be used to control the electric properties. If the value of the ME effect is high (dozens or hundreds of times higher than normal), it is called a giant ME effect.

The main use of the magnetoelectric effect is in variable and static magnetic field sensors. These sensors are used in navigation systems, electric motors, and also in vehicle ignition systems. Compared to similar devices based on the Hall effect or magnetoresistance, sensors based on the ME effect are more sensitive (according to research, up to one million times more sensitive) and they are also relatively cheap to manufacture.

The ME effect offers exciting possibilities for the use of multiferroics in new types of magnetic memory, e.g. ROM - read only memory. The ME effect could also potentially be used to create high-precision equipment for working with radiation in the microwave range, and to wirelessly transmit power to miniaturized electronic devices.

Bismuth ferrite

The subject of the study was bismuth ferrite (BiFeO3) - a highly promising multiferroic that is very promising in terms of its practical applications. It is planned to be used to create ultra energy-efficient magnetoelectric memory.

In addition, bismuth ferrite exhibits a magnetoelectric effect at room temperature, while in most other magnetoelectrics an ME effect of this magnitude is only observed at extremely low temperatures (below -160 degrees Celsius). Bismuth ferrite is an antiferromagnetic, which means that the magnetic moments of its magnetic sublattices (structures formed by atoms with the same parallel spins) cancel each other out, and the total magnetization of the material is close to zero. However, the spatial arrangement of the spins forms the same cycloidal spin structure (Fig. 1).

In the 1980s it was thought that this multiferroic exhibited only a quadratic magnetoelectric effect (i.e. polarization is quadratically proportional to the applied magnetic field). The fact that the linear magnetoelectric effect "went unnoticed" for a long time had to do with the spin cycloid (Fig. 1): due to the spin cycloid structure, certain characteristics, such as magnetization and the magnetoelectric effect "average out" to zero. However, when bismuth ferrite is placed in a strong magnetic field (greater than a certain critical value), the structure is destroyed and this is accompanied by the emergence of a linear ME effect (when polarization is linearly proportional to the applied field).

Early experiments indicated a low value of the linear magnetoelectric effect in bismuth ferrite (almost one thousand times lower than the actual value), however later experimental studies revealed a large ME effect and it was also demonstrated that by using it in layered structures, record values of the magnetoelectric effect can be achieved.

The authors of the paper developed a theoretical justification for the occurrence of the linear ME effect based on the Ginzburg-Landau theory and explained the previously large experimental value of the effect. As part of their theory, the researchers also showed that the ME effect could be enhanced in the presence of an electrostatic field.

Media Contact

Sergey Divakov
divakov@phystech.edu
7-925-834-0978

 @phystech

https://mipt.ru/english/ 

Sergey Divakov | EurekAlert!

More articles from Physics and Astronomy:

nachricht Quantum optics allows us to abandon expensive lasers in spectroscopy
22.11.2017 | Lomonosov Moscow State University

nachricht Nano-watch has steady hands
22.11.2017 | University of Vienna

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Corporate coworking as a driver of innovation

22.11.2017 | Business and Finance

PPPL scientists deliver new high-resolution diagnostic to national laser facility

22.11.2017 | Physics and Astronomy

Quantum optics allows us to abandon expensive lasers in spectroscopy

22.11.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>