From Lawrence Berkeley National Lab: “How to Catch a Magnetic Monopole in the Act”

Berkeley Logo

From Lawrence Berkeley National Lab

March 4, 2019
Theresa Duque
(510) 495-2418

Berkeley Lab-led study could lead to smaller memory devices, microelectronics, and spintronics

Magnetic monopoles in motion at 210 K. Red dots represent positive magnetic charges (north poles), while blue dots represent negative magnetic charges (south poles). (Credit: Farhan/Berkeley Lab)

A research team led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has created a nanoscale “playground” on a chip that simulates the formation of exotic magnetic particles called monopoles. The study – published recently in Science Advances – could unlock the secrets to ever-smaller, more powerful memory devices, microelectronics, and next-generation hard drives that employ the power of magnetic spin to store data.

Follow the ‘ice rules’

For years, other researchers have been trying to create a real-world model of a magnetic monopole – a theoretical magnetic, subatomic particle that has a single north or south pole. These elusive particles can be simulated and observed by manufacturing artificial spin ice materials – large arrays of nanomagnets that have structures analogous to water ice – wherein the arrangement of atoms isn’t perfectly symmetrical, leading to residual north or south poles.

This nanoscale “playground” on a chip uses nanomagnets to simulate the formation of exotic magnetic particles called “monopoles.” (Credit: Farhan/Berkeley Lab)

Opposites attract in magnetism (north poles are drawn to south poles, and vice-versa) so these single poles attempt to move to find their perfect match. But because conventional artificial spin ices are 2D systems, the monopoles are highly confined, and are therefore not realistic representations of how magnetic monopoles behave, said lead author Alan Farhan, who was a postdoctoral fellow at Berkeley Lab’s Advanced Light Source (ALS) at the time of the study, and is now with the Paul Scherrer Institute in Switzerland.


To overcome this obstacle, the Berkeley Lab-led team simulated a nanoscale 3D system that follows “ice rules,” a principle that governs how atoms arrange themselves in ice formed from water or the mineral pyrochlore.

“This is a crucial element of our work,” said Farhan. “With our 3D system, a north monopole or south monopole can move wherever it wants to go, interacting with other particles in its environment like an isolated magnetic charge would – in other words, like a monopole.”

A nanoworld on a chip

This XMCD (X-ray magnetic circular dichroism) image sequence recorded at 190 K shows how monopoles might form and move in response to changes in temperature. (Credit: Farhan/Berkeley Lab)

The team used sophisticated lithography tools developed at Berkeley Lab’s Molecular Foundry, a nanoscale science research facility, to pattern a 3D, square lattice of nanomagnets. Each magnet in the lattice is about the size of a bacterium and rests on a flat, 1-by-1-centimeter silicon wafer.

LBNL Molecular Foundry

“It’s a nanoworld – with tiny architecture on a tiny wafer,” but atomically configured exactly like natural ice, said Farhan.

To build the nanostructure, the researchers synthesized two exposures, each one aligned within 20 to 30 nanometers. At the Molecular Foundry, co-author Scott Dhuey fabricated nanopatterns of four types of structures onto a tiny silicon chip. The chips were then studied at the ALS, a synchrotron light source research facility open to visiting scientists from around the world. The researchers used a technique called X-ray photoemission electron microscopy (PEEM), directing powerful beams of X-ray light sensitive to magnetic structures at the nanopatterns to observe how monopoles might form and move in response to changes in temperature.

In contrast to PEEM microscopes at other light sources, Berkeley Lab’s PEEM3 microscope has a higher X-ray angle of incidence, minimizing shadow effects – which are similar to the shadows cast by a building when the sun strikes the surface at a certain angle. “In fact, the images recorded reveal no shadow effect whatsoever,” said Farhan. “This makes the PEEM3 the most crucial element to this project’s success.”

Farhan added that the PEEM3 is the only microscope in the world that gives users full temperature control in the sub-100 Kelvin (below minus 280 degrees Fahrenheit) range, capturing in real time how emergent magnetic monopoles form as artificial frozen ice melts into a liquid, and as liquid evaporates into a gas-like state of magnetic charges – a form of matter known as plasma.

The researchers now hope to pattern smaller and smaller nanomagnets for the advancement of smaller yet more powerful spintronics – a sought-after field of microelectronics that taps into particles’ magnetic spin properties to store more data in smaller devices such as magnetic hard drives.

Such devices would use magnetic films and superconducting thin films to deploy and manipulate magnetic monopoles to sort and store data based on the north or south direction of their poles – analogous to the ones and zeros in conventional magnetic storage devices.

The ALS and the Molecular Foundry are DOE Office of Science user facilities.

The work research was supported by the U.S. Department of Energy’s Office of Science, and the Swiss National Science Foundation.

See the full article here .


Please help promote STEM in your local schools.

Stem Education Coalition

Bringing Science Solutions to the World

In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

A U.S. Department of Energy National Laboratory Operated by the University of California.

University of California Seal

DOE Seal