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Me in the NCNR guide hall with the AC susceptometer we built. The smoke is just liquid nitrogen. Credit: J. Stoughton/NIST

SURFing from Susceptometers to Skyrmions: The Making of a Neutron MANiAC

Paul Neves, Summer Undergraduate Research Fellow, NIST Center for Neutron Research

I was a freshly minted senior in high school when I first came to the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). That day, my father had to drive me as I wouldn’t get my license for another few months, and I wore my most formal business casual outfit (I think it was one of three times I would wear a tie that summer). Now, four years later and a senior in college, my knowledge and love of physics and experience as a researcher have grown tremendously.

Still, I have a long way to go.

To be honest, when I was growing up I had no idea there was groundbreaking work being done just 20 minutes from my house. It wasn’t until my physics teacher Mr. Thompson at Wootton High School in Rockville, Maryland, shared some of what he learned at the NCNR through NIST’s Research Experience for Teachers program in class that I learned that the NCNR existed. While introducing us to modern physics, he explained how the researchers here exploit the quantum wave-like nature of neutrons to probe the structure and dynamics of a variety of atomic systems. Neutrons scatter off atoms in a sample like ocean waves scatter off the pylons on a pier. By detecting where these scattered neutrons end up, we can learn a lot about what the atoms in the sample are doing.

Graphical representation of the phonon eigenvectors and eigenstates of the atoms in a silicon crystal extracted by software I helped write during my high school internship. Credit: NIST

Upon learning this, I applied to the Summer High School Intern Program (SHIP) and requested to work at the NCNR because I thought that working with neutrons would be really cool. I spent the summer with Dan Parshall developing data analysis tools for large (we’re talking 40 GB, enough-to-make-the-server admins-upset large) inelastic neutron scattering data files. I learned a lot about the science of neutron scattering instruments and data interpretation. I also learned to use software that has not only helped me conduct research but also helped me fix my friends’ programs in school, learn other programming languages, build robots, probabilistically model board games to vanquish my foes, etc. But most importantly, I got a taste of what science is like overall — trying out new ideas, learning when and how to use new tools, exploring the unknown, and, oftentimes, making mistakes and failing. Thankfully, everyone at the NCNR was friendly and always happy to answer my many, many questions.

By the end of the summer, I helped create software that could extract the phonon eigenvectors and eigenstates — basically, the strengths, directions and frequencies of atomic vibrations in a crystal — in a way that uses all the available data from modern massive data sets. Tools like these can be used to gain deeper insights into subjects like the origins of high-temperature superconductivity.

After my experiences with this summer project and my amazing high school physics teachers, I realized I wanted to study physics in college.

SURF’s Up!

The first time I met one of my Summer Undergraduate Research Fellowship (SURF) advisors, Juscelino Leão, was when I was still in SHIP. Originally from Brazil, Juscelino is a very energetic guy with a penchant for wearing Hawaiian shirts. The 2014 World Cup was being held that summer, and he was very excited for Brazil to win … and crushed when they lost 7 to 1 to Germany in the semi-finals. What struck me — besides Brazil’s lack of defense — was just how culturally diverse the NCNR is. It seemed like just about every team had someone rooting for them.

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Me (center) with my advisers Juscelino Leao (left) and Nick Butch (right). Credit: NIST

After a year at the University of Maryland (UMD), I applied to be a SURF student, again at the NCNR. SURF is a great internship program that offers financial support to around 180 undergraduates every year across a wide range of disciplines (NCNR SURF students are fully supported by CHRNS, which is a partnership with the National Science Foundation). For my first project, I began working with Nick Butch and Juscelino on the construction of an AC susceptometer. Essentially, this device measures how strongly a sample responds to an applied magnetic field — a great tool for measuring changes in magnetic behavior. Once completed, guest researchers at the NCNR will be able to use it simultaneously with their neutron experiments to detect magnetic transitions in their samples under extreme conditions. And when I say “extreme,” I mean at temperatures colder than outer space and at pressures up to six times higher than at the bottom of the Mariana Trench.

One of the most important steps in making an AC susceptometer involves winding several coils with wire. The three coils needed for my design contained over 8,000 turns of wire in total, all of which had to be wrapped carefully and varnished between layers. After working for several weeks over a small repurposed lathe to make these coils, I learned ̶w̶h̶y̶ ̶t̶h̶e̶y̶ ̶h̶i̶r̶e̶d̶ ̶a̶n̶ ̶u̶n̶d̶e̶r̶g̶r̶a̶d̶u̶a̶t̶e̶ the important lesson that science often involves tedious and repetitious work. In fact, it took me so long to make these coils that at the end of the summer, when introducing my talk, my SURF director jokingly complained about how my project had made her office across the hall smell like varnish all summer.

Oh, what we do for science!

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The logo Rob Dimeo, director of the NCNR, came up with for the AC Susceptometer. I am on the left and Juscelino is on the right. I lovingly named it MANiACS. Credit: R. Dimeo/NIST
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On top is one of the hand-wrapped coils from the susceptometer. I wrote the number of turns, “3166,” so I wouldn’t forget about the experience, as if I could. All that wire, all that varnish. I can still smell it. Credit: J. Stoughton/NIST

Now Serving Skyrmions

As Nick is an adjunct assistant professor at UMD in addition to his role as an instrument scientist at the NCNR, I have been able to continue working with him year-round. We began working on synthesizing copper selenate, an interesting compound that hosts small, resilient magnetic vortices called skyrmions, which could one day be used in high-density data storage applications. Making samples is actually quite like baking, but with quartz tubes instead of pans and temperatures hot enough to turn any cake to ash. You add a little of this, a little of that, a pinch of zinc oxide, throw it in the furnace, and you’ve got yourself some tasty green skyrmion-containing powder (Warning: Do NOT eat the green skyrmion-containing powder). The skyrmion structures in copper selenate are topologically protected, which means that any information stored in them would be difficult to lose accidentally.

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Copper selenate, a skyrmion-containing compound, as synthesized at the Center for Nanophysics and Advanced Materials (CNAM) at the University of Maryland, College Park. Credit: Neves/NIST

I have also continued work on our AC susceptometer, turning it from a proof-of-concept prototype into a full-fledged piece of NCNR equipment. In September 2018, I will present the finished product at the 10th International Workshop on Sample Environment at Scattering Facilities in Potsdam, Germany. This comes two years after I showcased the prototype at the 9th workshop.

Working longer term has allowed me to take up some full-scale research projects between the AC susceptometer and the copper selenate skyrmion work. I have presented at conferences, and our first publication just got accepted. Working at NIST has been a great opportunity for professional development, and the people at the NCNR have made it a great place to work.

Despite how welcoming everyone is, NIST can be an intimidating place at first. Being a return SURFer and knowing the staff at the NCNR, I have been able to help the new interns feel more comfortable and confident. One of the ways I do this is by helping to instigate fun, team-building experiences. For instance, I can’t help but take some credit for last year’s holiday-sweater-themed after-seminar reception (in August) and (taking a cue from Juscelino’s wardrobe) our Hawaiian shirt-themed Fridays, which at this point might become a tradition.

Our turn for the NCNR kids to host the after-SURF-seminar reception. Note the winter-themed sweaters and decorations … in August. Credit: NIST

The Road Ahead

As a member of the NCNR staff said recently, “there’s no more new on [me].” I have met so many great people at the NCNR who have made me feel like I belong. Being a user facility, everyone is happy to help us students learn the tricks of the trade and get experience as researchers.

Now that I’m looking to apply to graduate school and enter a Ph.D. program, I have to consider what techniques, what field, I want to study. I honestly love condensed matter magnetism and scattering techniques, but only time will tell where I end up. The NCNR and the SURF program have allowed me to explore a range of projects and acquire a variety of techniques and requisite skills, and that experience will be invaluable to me as I make my decision.

This post originally appeared in Taking Measure, the official blog of the National Institute of Standards and Technology (NIST) on July 24, 2018.

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About the Author

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Paul Neves is a senior at the University of Maryland, College Park. He plans to obtain a Ph.D. in condensed matter physics and become a professor. Besides classes at UMD and research at the NCNR, Paul enjoys making and listening to music, playing tabletop games, volunteering with STEM outreach, watching sci-fi, and tinkering. As a tinkerer, Paul tries anything from car repair to chainmail weaving and is the proud owner of a chainmail tie (though he has no idea where to wear it).

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