Nav: Home

When 80 microns is enough

September 14, 2018

Should you care that scientists can control a baffling current? Their research results could someday affect your daily living.

Physicists have managed to send and control a spin current across longer distances than ever before - and in a material that was previously considered unsuitable for the task.

We'll return to what that strange sentence really means. But a spin current is a current that is kept going without relying on a simultaneous current of electrical charges.

"We've transferred spins more than 80 microns in an antiferromagnet," says Arne Brataas, a professor at the Norwegian University of Science and Technology's (NTNU) Department of Physics, and head of the university's recently launched Center for Quantum Spintronics (QuSpin).

Eighty microns - a mere 8/100 000th of a metre - is that so impressive?

"We're not exactly sending signals to the other side of the city. But this is far in the world of nanoelectronics," says Brataas.

Nanoelectronics forms the basis for all the smart technology we surround ourselves with.

Right about now you can start doing your happy dance. That's because 80 microns is getting to be a great enough distance to matter to people besides the scientists who are interested in knowledge for its own sake.

QuSpin has been collaborating with international physicists, including several in Germany and the Netherlands. The results are so intriguing that they are being published in the latest issue of the journal Nature.

So what is spintronics?

The technology of the future may depend on spintronics. If you don't know what it is, you might as well learn about it. But you can also jump ahead to the next section if you just want to learn about its practical uses.

Atoms have several parts. Electrons are the negatively charged particles, as many of us learned in science class.

But electrons don't only have a charge, they also have spin, an apparent internal rotation.

The spin has a direction, which is the basis of magnetism. A ferromagnetic material has a preference to align the spins in one particular direction. These materials are the magnets that you put on the refrigerator door.

Antiferromagnetic materials are also magnetic, but you don't notice their magnetic quality. The atoms in the material alternate between spins in opposite directions. These alterations effectively zero out the total spin so that the material itself does not have a magnetic moment. These materials don't work on your refrigerator door.

How spins are organized can therefore have very clear consequences for how a material behaves. The spin can be exploited.

Magnetism can transfer signals

Brataas and his colleagues aren't currently focusing so much on practical uses, so that's up to us to do.

Today's technology transmits signals in a computer's microchips by means of an electric charge. In an electrical current, electrons and spin both flow through the material.

But in the future a spin current will be able do parts of the same job, using magnetism to transmit the signals instead, without electrons passing through with the current.

What are the benefits of spin currents?

Well, for one, a spin current can sometimes flow more readily than an electrical charge current, since only the spin moves and not the electrons. This results in less energy loss in transmitting the signal.

A spin current does not generate a lot of heat. As the transistors on microchips have become ever smaller, overheating has become a growing problem, causing microchips to melt. Using spin current means smaller transistors can be used -another practical feature as new electronic gizmos pop up everywhere.

Spin current can also be controlled much more quickly. So all the new gizmos can be a lot faster.

Controlling spin current

These results would not be nearly as exciting if physicists couldn't control the spin current at the same time. But they can.

Physicists can start the spin current by applying an electric field at one end of the material. The signal flows through the material without the electrons moving from one end to the other.

Physicists can also do the opposite at the other end, and transfer the spin current to an electrical current.

They have managed to do this at temperatures approaching room temperature. Granted, 200 degrees Kelvin - or -73.15 degrees Celsius - is a bit chilly for a room, but it falls within the range of naturally occurring temperatures on Earth. The researchers expect that they will be able do this experiment at a more comfortable room temperature pretty soon as well.

The research group used the antiferromagnet hematite, an iron oxide (Fe2O3), in their experiments.

The results this time are clearly just a step along the way. The research team will continue to test other materials and look at how these materials respond to different types of influences.

High risk, but important

NTNU's QuSpin was awarded Norwegian Centre of Excellence (SFF) status last year, a highly regarded recognition. The centre was created to combine theory with experimental physics in the spintronics field and can already show world-leading results.

"The centre focuses on high risk projects of major importance in many different directions," says Brataas.

The status that SFF confers provides more stable research funding, since QuSpin is guaranteed support for ten years. The funding facilitates high-risk research that can fail too. And they do, all the time.

Many of their experiments do not match the theories or vice versa, and that is important in its own way. But some experiments are spot on, and they can have particularly great significance.
-end-
International cooperation

SFF status has also provided greater opportunities for collaborating with other top researchers. You don't receive SFF status without having already shown that you can perform at the very highest level within the field of study.

The key researchers are all affiliated with QuSpin at NTNU in either full-time or part-time positions.

NTNU has contributed significantly to the theoretical basis for the experiments. Researcher Alireza Qaiumzadeh has been central to this work, as has Associate Professor Rembert Duine at Utrecht University in the Netherlands.

The experiments themselves were carried out at the Johannes Gutenberg University Mainz, where Professor Mathias Klaeui oversees them. Both Duine and Klaeui are affiliated with QuSpin through part-time positions at NTNU.

In addition to the SFF status, which provides more predictable funding for the research group, Brataas has also been awarded an ERC Advanced Grant of NOK 19 million from the European Research Council.

Reference: Lebrun, R; Ross, A; Bender, S. A.; Qaiumzadeh, Alireza; Baldrati, L.; Cramer, J.; Brataas, Arne; Duine, R. A.; Kläui, M.. (2018) Tunable long-distance spin transport in a crystalline antiferromagnetic iron oxide. Nature. vol. 561 (7722).

Norwegian University of Science and Technology

Related Electrons Articles:

Deceleration of runaway electrons paves the way for fusion power
Fusion power has the potential to provide clean and safe energy that is free from carbon dioxide emissions.
Shining light on low-energy electrons
The classic method for studying how electrons interact with matter is by analyzing their scattering through thin layers of a known substance.
Ultrafast nanophotonics: Turmoil in sluggish electrons' existence
An international team of physicists has monitored the scattering behavior of electrons in a non-conducting material in real-time.
NASA mission uncovers a dance of electrons in space
NASA's MMS mission studies how electrons spiral and dive around the planet in a complex dance dictated by the magnetic and electric fields, and a new study revealed a bizarre new type of motion exhibited by these electrons.
'Hot' electrons don't mind the gap
Rice University scientists discover that 'hot' electrons can create a photovoltage about a thousand times larger than ordinary temperature differences in nanoscale gaps in gold wires.
Electrons used to control ultrashort laser pulses
We may soon get better insight into the microcosm and the world of electrons.
Supercool electrons
Study of electron movement on helium may impact the future of quantum computing.
Two electrons go on a quantum walk and end up in a qudit
There is a variety of physical systems that can be used to implement a separate quantum bit, but significantly less research has been done into systems of several qubits or qudits.
Radiation that knocks electrons out and down, one after another
Researchers at Japan's Tohoku University are investigating novel ways by which electrons are knocked out of matter.
Controlling electrons in time and space
A new method has been developed to control electrons being emitted from metal tips.

Related Electrons Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...