Magnetics Business & Technology - May/June 2023 - 66

VISIONS
Magnetic Quantum Material Broadens Platform for Probing Next-Gen Information
Technologies
Scientists at the Department
of Energy's
Oak Ridge National
Laboratory used
neutron scattering to
determine whether
a specific material's
atomic structure could
host a novel state of
matter called a spiral
spin liquid. By tracking
tiny magnetic moments
known as " spins " on
the honeycomb lattice of a layered iron trichloride magnet, the
team found the first 2D system to host a spiral spin liquid.
The discovery provides a test bed for future studies of physics
phenomena that may drive next-generation information technologies.
These include fractons, or collective quantized vibrations
that may prove promising in quantum computing, and
skyrmions, or novel magnetic spin textures that could advance
high-density data storage.
" Materials hosting spiral spin liquids are particularly exciting
due to their potential to be used to generate quantum spin
liquids, spin textures and fracton excitations, " said ORNL's
Shang Gao, who led the study published in Physical Review
Letters.
A long-held theory predicted that the honeycomb lattice can
host a spiral spin liquid - a novel phase of matter in which spins
form fluctuating corkscrew-like structures.
Yet, until the present study, experimental evidence of this
phase in a 2D system had been lacking. A 2D system comprises
a layered crystalline material in which interactions are
stronger in the planar than in the stacking direction.
Gao identified iron trichloride as a promising platform for testing
the theory, which was proposed more than a decade ago.
He and co-author Andrew Christianson of ORNL approached
Michael McGuire, also of ORNL, who has worked extensively
on growing and studying 2D materials, asking if he would
synthesize and characterize a sample of iron trichloride for
neutron diffraction measurements. Like 2D graphene layers
exist in bulk graphite as honeycomb lattices of pure carbon,
2D iron layers exist in bulk iron trichloride as 2D honeycomb
layers. " Previous reports hinted that this interesting honeycomb
material could show complex magnetic behavior at low
temperatures, " McGuire said.
" Each honeycomb layer of iron has chlorine atoms above and
below it, making chlorine-iron-chlorine slabs, " McGuire said.
" The chlorine atoms on top of one slab interact very weakly
with the chlorine atoms on the bottom of the next slab through
van der Waals bonding. This weak bonding makes materials
like this easily peeled apart into very thin layers, often down to
a single slab. This is useful for developing devices and understanding
the evolution of quantum physics from three dimensions
to two dimensions. "
66 Magnetics Business & Technology * May/June 2023
In quantum materials, electron spins can behave collectively
and exotically. If one spin moves, all react - an entangled state
Einstein called " spooky action at a distance. " The system stays
in a state of frustration - a liquid that preserves disorder because
electron spins constantly change direction, forcing other
entangled electrons to fluctuate in response.
The first neutron diffraction studies of ferric chloride crystals
were performed at ORNL 60 years ago. Today, ORNL's extensive
expertise in materials synthesis, imaging, neutron scattering,
theory, simulation and computation enables pioneering
explorations of magnetic quantum materials that drive development
of next-generation technologies for information security
and storage.
Mapping spin movements in the spiral spin liquid was made
possible by experts and tools at the Spallation Neutron Source
and the High Flux Isotope Reactor, DOE Office of Science
user facilities at ORNL. ORNL co-authors were essential for
the success of the neutron scattering experiments: Clarina
dela Cruz, who led experiments using HFIR's POWDER
diffractometer; Yaohua Liu, who led experiments employing
SNS's CORELLI spectrometer; Matthias Frontzek, who led
experiments engaging HFIR's WAND2 diffractometer; Matthew
Stone, who led experiments operating SNS's SEQUOIA
spectrometer; and Douglas Abernathy, who led experiments
working SNS's ARCS spectrometer.
" The neutron scattering data from our measurements at SNS
and HFIR provided compelling evidence of a spiral spin liquid
phase, " Gao said.
" The neutron scattering experiments measured how the
neutrons exchange energy and momentum with the sample,
allowing the magnetic properties to be inferred, " said co-author
Matthew Stone. He described the magnetic structure of a spiral
spin liquid: " It looks like a topographic map of a group of mountains
with a bunch of rings going outward. If you were to walk
along a ring, all spins would point in the same direction. But if
you walk outward and cross different rings, you're going to see
those spins begin to rotate about their axes. That's the spiral. "
" Our study shows that the concept of a spiral spin liquid is viable
for the broad class of honeycomb lattice materials, " said
co-author Andrew Christianson. " It gives the community a new
route to explore spin textures and novel excitations, such as
fractons, that then may be used in future applications, such as
quantum computing. "
The title of the paper is " Spiral Spin Liquid on a Honeycomb
Lattice. " DOE's Office of Science supported the work.
UT-Battelle manages ORNL for the Department of Energy's Office
of Science, the single largest supporter of basic research
in the physical sciences in the United States. The Office of
Science is working to address some of the most pressing challenges
of our time.
For more information, please visit energy.gov/science.
www.MagneticsMag.com
http://energy.gov/science http://www.MagneticsMag.com
Magnetics Business & Technology - May/June 2023

Table of Contents for the Digital Edition of Magnetics Business & Technology - May/June 2023
