Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers flip the script on magnetocapacitance

01.06.2017

Capacitors, electronic components that store and quickly release a charge, play an important role in many types of electrical circuits. They'll play an equally important role in next-generation spintronic devices, which take advantage of not only electron charge but also spin -- the tiny magnetic moment of each electron.

Two years ago, an international team of researchers showed that by manipulating electron spin at a quantum magnetic tunneling junction -- a nanoscale sandwich made of two metal electrodes with an insulator in the middle -- they could induce a large increase in the junction's capacitance.


The crystal structure of Fe3O4 and Fe electrodes analyzed by RHEED (reflection high energy electron diffraction). The patterns indicate that Fe3O4 has the inverse spinel structure with the same crystal orientation of the MgO substrate, while Fe takes polycrystalline structure.

Credit: Kaiju et. al.

Now, that same research team has flipped the script on the phenomenon, known as magnetocapacitance. In a paper published in the journal Scientific Reports, they show that by using different materials to build a quantum tunneling junction, they were able to alter capacitance by manipulating spins in the opposite way from "normal" magnetocapacitance. This inverse effect, the researchers say, adds one more potentially useful phenomenon to the spintronics toolkit.

"It gives us more parameter space to design devices," said Gang Xiao, chair of the physics department at Brown and one of the paper's coauthors. "Sometimes normal capacitance might be better; sometimes the inverse might be better, depending on the application. This gives us a bit more flexibility."

Magnetocapacitors could be especially useful, Xiao says, in making magnetic sensors for a range of different spintronic devices, including computer hard drives and next-generation random access memory chips.

The research was a collaboration between Xiao's lab at Brown, the lab of Hideo Kaiju and Taro Nagahama at Japan's Hokkaido University and the lab of Osamu Kitakami at Tohoku University.

Xiao has been investigating magnetic tunneling junctions for several years. The tiny junctions can work in much the same way as capacitors in standard circuits. The insulator between the two conducting electrodes slows the free flow of current across the junction, creating resistance and another phenomenon, capacitance.

But what makes tunneling junctions especially interesting is that the amount of capacitance can be changed dynamically by manipulating the spins of the electrons within the two metal electrodes. The electrodes are magnetic, meaning that electrons spinning within each electrode are pointed in one particular direction. The relative spin direction between two electrodes determines how much capacitance is present at the junction.

In their initial work on this phenomenon, Xiao and the research team showed just how large the change in capacitance could be. Using electrodes made of iron-cobalt-boron, they showed that by flipping spins from anti-parallel to parallel, they could increase capacitance in experiments by 150 percent. Based on those results, the team developed a theory predicting that, under ideal conditions, the change in capacitance could actually go as high as 1,000 percent.

The theory also suggested that using electrodes made from different types of metals would create an inverse magnetocapacitance effect, one in which anti-parallel spins create more capacitance than parallel spins. That's exactly what they showed in this latest study.

"We used iron for one electrode and iron oxide for the other," Xiao said. "The electrical properties of the two are mirror images of each other, which is why we observed this inverse magnetocapacitance effect."

Xiao says the findings not only suggest a larger parameter space for the use of magnetocapacitance in spintronic devices, they also provide important verification for the theory scientists use to explain the phenomenon.

"Now we see that the theories fit well with the experiment, so we can be confident in using our theoretical models to maximize these effects, either the 'normal' effect or the inverse effect that we have demonstrated here," Xiao said.

###

The work was supported by the National Science Foundation (DMR-1307056), the Japan Society for the Promotion of Science (Grant-in-Aid for Scientific Research (B), 15H03981), the Japanese Ministry of Education, Culture, Sports, Science and Technology (Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials) and the Center for Spintronics Research Network at Tohoku University.

Release issued jointly Brown University, Tohoku University and Hokkaido University

Media Contact

Kevin Stacey
401-863-3766

 @brownuniversity

http://news.brown.edu/ 

Kevin Stacey | 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
23.11.2017 | 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: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

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....

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

Water cooling for the Earth's crust

23.11.2017 | Earth Sciences

Nano-watch has steady hands

23.11.2017 | Physics and Astronomy

Batteries with better performance and improved safety

23.11.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>