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Revealing the Thermal Heat Dance of Magnetic Domains

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Newswise — UPTON, NY—Everyone knows that holding two magnets together will lead to one of two results: they stick together, or they push each other apart. From this perspective, magnetism seems simple, but scientists have struggled for decades to really understand how magnetism behaves on the smallest scales. On the near-atomic level, magnetism is made of many ever-shifting kingdoms—called magnetic domains—that create the magnetic properties of the material. While scientists know these domains exist, they are still looking for the reasons behind this behavior.

Now, a collaboration led by scientists from the U.S. Department of Energy’s Brookhaven National Laboratory, Helmholtz-Zentrum Berlin (HZB), the Massachusetts Institute of Technology (MIT), and the Max Born Institute (MBI) published a study in Nature in which they used a novel analysis technique—called coherent correlation imaging (CCI)—to image the evolution of magnetic domains in time and space without any previous knowledge. The scientists could not see the “dance of the domains” during the measurement but only afterward, when they used the recorded data to “rewind the tape.”

The “movie” of the domains shows how the boundaries of these domains shift back and forth in some areas but stay constant in others. The researchers attribute this behavior to a property of the material called “pinning.” While pinning is a known property of magnetic materials, the team could directly image for the first time how a network of pinning sites affects the motion of interconnected domain walls.

“Many details about the changes in magnetic materials are only accessible through direct imaging, which we couldn’t do until now. It’s basically a dream come true for studying magnetic motion in materials,” said Wen Hu, scientist at the National Synchrotron Light Source II (NSLS-II) and co-corresponding author of the study.

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The researchers expect CCI to help unlock other properties of the microcosm of magnetism—such as degrees of freedom or hidden symmetries—that previously weren’t accessible through other techniques. CCI’s usefulness also represents a breakthrough beyond magnetic materials since the technique can be transferred to different measurement techniques and research areas. One area that might benefit the most from understanding the movement of magnetic domains on the nanoscale (one nanometer is 0.000000038 inches!) is novel computing. Novel memory technology could leverage special magnetic domains called “skyrmions.”

“Skyrmions are interesting for artificial intelligence computing because they possess a property that is similar to our short-term memory,” said Felix Büttner, group leader at Helmholtz-Zentrum Berlin, professor at the University of Augsburg and co-corresponding of the study. “In current computing architectures everything is linear, which means that the memory is separated from the processor. This is not an issue for most applications but, for example, it makes speech recognition difficult. In speech recognition, the computing part only processes the incoming words, but doesn’t remember what has been said previously. In addition, sending that information back from the memory takes a lot of energy. By using skyrmions, we may be able to harness their short-term memory in some way and avoid these issues.”

However, before engineers and scientists can develop technology that uses this feature, they first need to understand how to manipulate skyrmions and other magnetic domains. This was the intention when the collaboration between NSLS-II, Geoffrey Beach’s group at MIT, and MBI formed. They wanted to investigate how skyrmions in their magnetic devices reacted to external stimuli, specifically in an external magnetic field. HZB joined the collaboration when Büttner moved from MIT to Berlin.

“In 2018, we had measurement time at the Coherent Soft X-ray Scattering (CSX) beamline at NSLS-II; however, the experimental chamber we wanted to use wasn’t ready. That meant we didn’t have the external magnetic field, but we had a back-up plan for studying the thermal motion,” said Hu, who is part of the CSX beamline team.

Büttner added, “I expected this experiment would be another demonstration experiment but nothing more. To be honest, I was surprised we saw thermal motion at all. We studied the same device at room temperature and barely saw any thermal motion. This time we studied it at 310 Kelvin, which is about 98 Fahrenheit, and we saw so much more. That was surprising! And it was just the beginning.”

How a back-up plan leads to hidden insights

In their experiment, the team used coherent x-rays from the CSX beamline to take a series of snapshots of the magnetic domains. CSX is part of the advanced suite of research tools available at NSLS-II for studying materials. The research team used the beamline in a holography setup to take the images. In most holography experiments, scientists take one image every three to four seconds, however, the fast detector at the CSX beamline allowed the team to take up to 100 images per second.

“After the measurement, we started a normal data analysis by adding up 200 images. Once we did this, we realized that the system changed much faster than we expected. The temperature really influenced the physics in the sample,” said Christopher Klose, PhD student at MBI and first author of the study. “That was a real surprise and the beginning of us developing our post-processing technique—coherent correlation imaging (CCI)—so that we could resolve this fast movement.”

After this initial realization, the team decided to dig deeper into the data. They knew that the details about the domain movements were encoded in their data. While there was no existing data analysis technique to solve their problem, they were able to find algorithms that could be adapted. Over the course of three years, the team developed the new algorithm that powers the novel CCI technique.

“There were a lot of challenges. To develop CCI, we combined known correlation function analysis from x-ray photon correlation spectroscopy (XPCS) with holography, which is an imaging technique. One issue was that the holography data was not suited for XPCS analysis,” said Klose.

When x-rays hit the samples in these experiments, they scatter both on the magnetic domains and a holographic mask that defines the field of view. The detector records all the scattered x-rays regardless of their origin. But the team is only interested in magnetic scattering. So, they needed to clean up the data before they could calculate the correlation functions.

“Once we had the correlation function, we could compare all those frames to each other to find similar ones. That also required a new algorithm because we had almost 30,000 frames to sort through,” continued Klose.

This challenge required an algorithm that could catalog the states of the domains for each frame. This algorithm would be a real game-changer for this task because it would be able to sort these states in ways no human could achieve.

How pinning shapes the magnetic landscape

After the team had sorted through their data using CCI, they went to work on the interpretation. The reconstructed images showed black and white domains scattered across their device. But some of these borders, or domain walls, shifted back and forth between the frames, while others mostly stayed put. The question: what were the researchers seeing and what did this mean for skyrmions and magnetic domains?

“Skyrmions are small spherical objects, comparable to balls on a pool table. In our case, thermal energy makes them wander around the table. Now, if the pool table has pinning, the surface isn’t smooth but instead is a hilly landscape. We have two kinds of pinning sites: attractive ones and repulsive ones. The first ones are valleys, and the second ones are hills. In that case, the skyrmions would rest in the “attractive” valleys. If they wanted to move around, they would need to overcome the slopes of the “repulsive” hills,” said Büttner.

The researchers found that domain walls behave like rubber bands. They can be pinned down and then oscillate back and forth like a guitar string. While attractive sites can accommodate domain walls, repulsive sites inhibit the movement of domain walls. A domain wall would need to be lifted over the repulsive site. It cannot wander through it. This explains why the scientists saw some domain walls shift constantly, while other barely moved. The latter ones were surrounded by repulsive sites.

“CCI gave us the tool to see this movement over time. Basically, we could make a little movie on how these domains shift. This experiment allowed us to see this kind of fluctuating behavior and its cause for the first time,” said Hu. “We didn’t expect that this collaboration would lead to the invention of a new technique that would broadly benefit other users and researchers studying dynamics.”

Büttner added, “We needed almost a year to fully understand the physics we had found and develop an explanation for the dynamics that we saw. In hindsight, the experiment itself was the easiest part of it all. The real work was the technique development and then the physics explanation.”

The researchers agreed that one key ingredient for this breakthrough was the diverse team of experts they had assembled for this task. They hope that many other research groups will benefit from CCI. While they prepare for applying CCI to a broader range of previously inaccessible dynamics as well as expanding the technique to other x-ray sources, they’re also working on implementing machine learning to make the CCI analysis less manual and more accessible by an even broader community.

The team for this work consisted of Christopher Klose, Michael Schneider, Stefan Eisebitt and Bastian Pfau from the Max Born Institute, Felix Büttner and Riccardo Battistelli from the Helmholtz-Zentrum Berlin, Wen HuClaudio MazzoliAndi Barbour and Stuart B. Wilkins from the National Synchrotron Light Source II at Brookhaven National Laboratory, Kai Litzius, Ivan Lemesh, Jason M. Bartell, Mantao Huang and Geoffrey S.D. Beach from the Massachusetts Institute of Technology, Christian M. Günther from the Technische Universität Berlin.

NSLS-II is a U.S. Department of Energy (DOE) Office of Science user facility located at DOE’S Brookhaven National Laboratory.

This work was supported by the DOE Office of Science.

Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Follow @BrookhavenLab on Twitter or find us on Facebook.

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Kemptville author’s book being sent to the moon

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One of Michael Blouin’s books is going to be launched into space on a microdisk and stay on the surface of the moon. (Submitted by Michael Blouin)

An author from North Grenville, Ont., is going to be part of a small club of authors whose works will be sent to the moon.

Michael Blouin of Kemptville says he’s been interested in space travel since the Apollo 11 mission that landed humans on the moon for the first time.

To be part of a group of hundreds of authors having their work immortalized within the vast expanse of space has him “gobsmacked.”

“I take comfort in the fact that no matter what happens, it looks like my books … will survive and be there,” he said.

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“I sometimes wake up at night and say ‘Oh yeah, I’m going to the moon. Wow.’ It’s kind of amazing.”

How it came to be

Blouin said he’s been a lifelong fan of NASA and space exploration, so when the opportunity to get his work in the Writers on the Moon project came up, he had to take it.

Then around the deadline to apply, his house burned down.

Amid the chaos of not having anywhere to live and then moving into his son’s house, he realized he’d missed his chance.

“I had missed the deadline to apply for this program for books to go to the moon by 12 hours and I was just kicking myself,” he said.

“I lost everything and now I’d missed out on my chance to do something I’d always dreamed about doing.”

Luckily a friend and author in Newfoundland, Carolyn R. Parsons, said she had managed to get some of her work included in the project and had enough space on her microdisk to include him as well.

A rocket sits upright.
This rocket will carry a lander and books from a couple hundred authors up to the moon. (United Launch Alliance)

When do the books go?

The NASA launch is scheduled for Feb. 25 at Cape Canaveral in Florida, which will see his book Skin House brought to the stars along with other works of independent fiction.

Blouin is getting the chance to see the launch.

“These launches sometimes get delayed due to technical reasons or due to weather,” he said.

“But I’m hoping to give myself a big enough window that I’ll actually be on site.”

Blouin had some advice for people who aspire to write or create.

“Any young person aspiring in the arts just shouldn’t give up. Keep trying,” he said. “It can be a tough go but it’s worth every moment.”

He’s getting another of his books — I am Billy the Kid — up to the moon in 2024.

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Green comet zooming our way, last visited 50,000 years ago – Cochrane Today

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CAPE CANAVERAL, Fla. (AP) — A comet is streaking back our way after 50,000 years.

The dirty snowball last visited during Neanderthal times, according to NASA. It will come within 26 million miles (42 million kilometers) of Earth Wednesday before speeding away again, unlikely to return for millions of years.

So do look up, contrary to the title of the killer-comet movie “Don’t Look Up.”

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Discovered less than a year ago, this harmless green comet already is visible in the northern night sky with binoculars and small telescopes, and possibly the naked eye in the darkest corners of the Northern Hemisphere. It’s expected to brighten as it draws closer and rises higher over the horizon through the end of January, best seen in the predawn hours. By Feb. 10, it will be near Mars, a good landmark.

Skygazers in the Southern Hemisphere will have to wait until next month for a glimpse.

While plenty of comets have graced the sky over the past year, “this one seems probably a little bit bigger and therefore a little bit brighter and it’s coming a little bit closer to the Earth’s orbit,” said NASA’s comet and asteroid-tracking guru, Paul Chodas.

Green from all the carbon in the gas cloud, or coma, surrounding the nucleus, this long-period comet was discovered last March by astronomers using the Zwicky Transient Facility, a wide field camera at Caltech’s Palomar Observatory. That explains its official, cumbersome name: comet C/2022 E3 (ZTF).

On Wednesday, it will hurtle between the orbits of Earth and Mars at a relative speed of 128,500 mph (207,000 kilometers). Its nucleus is thought to be about a mile (1.6 kilometers) across, with its tails extending millions of miles (kilometers).

The comet isn’t expected to be nearly as bright as Neowise in 2020, or Hale-Bopp and Hyakutake in the mid to late 1990s.

But “it will be bright by virtue of its close Earth passage … which allows scientists to do more experiments and the public to be able to see a beautiful comet,” University of Hawaii astronomer Karen Meech said in an email.

Scientists are confident in their orbital calculations putting the comet’s last swing through the solar system’s planetary neighborhood at 50,000 years ago. But they don’t know how close it came to Earth or whether it was even visible to the Neanderthals, said Chodas, director of the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory in California.

When it returns, though, is tougher to judge.

Every time the comet skirts the sun and planets, their gravitational tugs alter the iceball’s path ever so slightly, leading to major course changes over time. Another wild card: jets of dust and gas streaming off the comet as it heats up near the sun.

“We don’t really know exactly how much they are pushing this comet around,” Chodas said.

The comet — a time capsule from the emerging solar system 4.5 billion years ago — came from what’s known as the Oort Cloud well beyond Pluto. This deep-freeze haven for comets is believed to stretch more than one-quarter of the way to the next star.

While comet ZTF originated in our solar system, we can’t be sure it will stay there, Chodas said. If it gets booted out of the solar system, it will never return, he added.

Don’t fret if you miss it.

“In the comet business, you just wait for the next one because there are dozens of these,” Chodas said. “And the next one might be bigger, might be brighter, might be closer.”

___

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

Marcia Dunn, The Associated Press

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How to spot the planets hiding in plain sight – CBC.ca

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This video was produced by Trevor Kjorlien as part of the CBC Creator Network. Learn more about the Creator Network here.

Most people are aware that if you live in the city, light pollution limits your view of the night sky. If you want to see lots of stars, comets and the Milky Way, you have to get out into the countryside, where the sky is dark.

However noble the cause, awareness campaigns to educate people about light pollution have had an unintended side effect: people think you can’t see anything in the urban night sky except a handful of bright stars and the moon.

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So if you are a city dweller and you don’t look up, what are you missing out on?

The planets.

Even in the most light-polluted skies, we can see five planets with the naked eye: Mercury, Venus, Mars, Jupiter and Saturn.

If you’d been walking through Montreal’s Jeanne-Mance Park in the early morning of June 26, 2022, you would have seen the planet Venus above the city skyline, next to the crescent moon. (Trevor Kjorlien/CBC Creator Network)

How to find the planets

It’s not unusual to be able to see the planets. Normally, some appear in the evening and some in the morning, depending on where they are in their orbit around the sun.

How do you know when and where to look?

In June 2022, we had a rare opportunity: all the naked-eye planets were visible in the early morning. At dawn, you could see all five of them lined up before the sun rose and washed their light away.

Why did they appear to line up, as they did then?

The sun rises in the east and sets in the west. In the northern hemisphere, the sun appears to move through the sky in the south.

Now imagine a line was drawn out behind the sun as it travels in the sky through the day. Astronomers call this “the path of the ecliptic.”

In a rare sight, the planets lined up in the southern sky above downtown Montréal on the early morning of June 26, 2022, roughly following the path of the ecliptic. (Trevor Kjorlien/CBC Creator Network)

At night, you can roughly follow this imaginary line, and that’s where the planets can be found. This is because the planets all orbit the Sun on the same plane, much like a frisbee or a vinyl record. Because all the planets travel more or less on the same plane, from our view on Earth, they appear to line up and are always visible in the southern sky from the northern hemisphere.

Embedded in our daily lives

We can see seven significant celestial objects with the naked eye: the sun, the moon and the five planets closest to the sun.

Test yourself: what day are you reading this article? Which celestial object does this day refer to? (Trevor Kjorlien/CBC Creator Network)

Where else do we see the number seven in our day-to-day lives?

In the calendar.

Through the magic of myth and etymology, each day of the week corresponds to these celestial objects.

  • Monday is moon day, named for the moon. (In French, la lune becomes lundi.)
  • Tuesday, named for Tiw, the Germanic god of war, corresponds to the Roman war god Mars (in French, mardi).
  • Wednesday is named for Woden, the Germanic god corresponding to the Roman god Mercury (in French, mercredi).
  • Thursday is named for Thor, the Norse god corresponding to the Roman god Jupiter. (In French, from the Latin Jovis, a name for Jupiter, we get jeudi.)
  • Friday is named for Frigga, the Germanic goddess corresponding to the Roman goddess of love, Venus (in French, vendredi).
  • Saturday is named for Saturn.
  • Sunday is named for the sun.

Think about which day you’re reading this. Which celestial object does it correspond to?

Not only are the planets hiding in plain sight in the urban night sky, they’re hiding in our calendars — embedded in our daily lives.


The Creator Network, which works with emerging visual storytellers to bring their stories to CBC platforms, produced the piece. If you have an idea for the Creator Network, you can send your pitch here.

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